Was the Macedonian tongue a greek dialect or not?

Yes it was a greek (Doric) dialect.
We shall break this discussion into two parts. The first one consists of evidence found prior to the excavations in Vergina by the late Professor Manolis Andronikos. The second one consists of evidence found mainly since then. This evidence leads beyond any doubt to the conclusion that the Macedonians spoke a greek dialect which was basically a Doric one, it borrowed words and was influenced by the Aeolic dialect spoken by the Thessalians neighbors of Macedonians, and also borrowed few words of Phrygic and Illyrian origin.
The Thessalians (Aeolic) influence convinced some researchers that the genealogy of Makedon given by Hellanikos (see Question 3) was more accurate than that given by Hesiodos.
In the volume "Macedonia: 4000 years of Greek history and civilization" Professor M. Sakellariou examined the words known to be unique in the Macedonian dialect of greek and related their root to the roots of words of other Greek dialects. Summarizing, many of the words that were previously considered of non-Greek origin were also in (rare) use in other parts of Greece.
There have been made various claims that the Macedonians up to some time in the 4th century BC used to speak a non-Greek language and at that time (around 340BC) were 'hellenized' by the Athenians and thus learned how to speak the attic dialect. These claims can be easily proved to be totally false even if one uses only pre-Vergina evidence.
Below we present various views on the topic.
Pre-Vergina evidence.
Fr. Sturz (in "De Dialecto Macedonica et Alexandrina", 1808) concluded that the Macedonian tongue was a greek Doric dialect. August Flick, O. Hoffmann, Otto Abel, and Karl Belloch, as well as George Busolt, Fritz Geyer, Ulrich Wilcken, Helmuth Berve, Gustave Glotz, P. Roussel, P Pouquet, A Jarde, R Cohen, J. Bury, St. Casson, W. Heurtley, D. Hogarth, J. de Waele, just to name a few (non-Greek) historians and archaeologists, shared the same views.
On the other hand, there were some historians and writers such as M. Vasmer (Revue du ministere d' instruction publique de Russie, 1908), P Kretschmer and Bulgarians G. Kazarow and Vlad. Georgiev that rejected this thesis. Georgiev attempted to show that Macedonians were member of a Thracoillyrian nation thus speaking Illyrian, a non-greek language. That this was not the case was shown in Question 6. G Weigand also shared the opinions of these authors. G. Hatzidakes rejected these theses in various texts and among them in "Zur Abstammung der alten Makedonier (eine ethnologische Studie)". For more details we refer to Daskalakis (page 104).
Coins found in Macedonia have inscriptions in greek and are dated from the early 5th BC century. Such found coins are the following ones.
An octadrachm of Alexander I (circa 478BC).
Coins from the reign of Archelaos (413-399BC) and Amyntas III (393-370BC).
the ring of Sindos with the word Gk:'DVRON' (Gift) dated around 480BC.
These coins are dated well before 340BC, the time of the alleged "hellenization" of Macedonians.
Macedonians had their own month names. If one accepts the thesis that Macedonian were 'hellenized' by the Athenians some time around 340BC hen one can safely assume that these names must be identical to those used by the Athenians. If not, they would show the linguistic roots of the Macedonians prior to their alleged who claimed that Dorians and Macedonians belonged to the same tribe (Herodotus claimed that the Macedonians who descended to southern Greece after crossing Doris became known as Dorians) and thus Macedonians were a Greek tribe, the month names of Macedonians were Greek and were different from the ones used by the Athenians. The list of these names used by the Macedonians and the list of month names of the Lacedaemonians (who were Dorians) have a common intersection, the names Artemisios and Apellaios.
Persians when first occupied Macedonia during their conquests in Europe around 510-480BC described the people living in Macedonia as "The Greeks wearing a shield-like hat" and who were non other than the Macedonians themselves. This incident occurred long before the alleged "hellenization" of Macedonians.
It is believed that the worship of the 12 Olympian Gods had started in Macedonia (as related to their place of "residence". Mountain Olympus is located in Pieria and both these names are Greek. It is claimed the magnificent view of Mt. Olympus when viewed from Macedonia, while its view from the south (Thessaly) is hindered by other mountains, inspired the Macedonians and from the other Greeks to consider this mountain the residence of their Gods.
Athenian comedies used to make fun of the idioms and the dialects of other Greeks like those of Spartans, Boeoteans and of course Macedonians. Some time in the 5th century BC a comedy entitled "Pausanias or Macedonians?" written by the Athenian Strattis was played in Athens. In various parts of this comedy a Macedonian explains how various words of the attic dialect are called in the Macedonian dialect.
It can be inferred from these references that Macedonians spoke a Doric Greek dialect. In a work of the ancient writer Athenaios, one can find samples of the work of Strattis. In an article written by A. Koerte quoting Athenaios VII,323b we can find in that comedy of Strattis the following conversation:
"STRATTIS GOYN EN MAKEDOSIN EROMENOU TINOS ATTIKOY VS AGNOOYNTOS TO ONOMA KAI LEGONTOS: H SFYRAINA D' ESTI TIS;" FHSIN O ETEROS " KESTRAN MEN YMMES VTTIKOI KIKLHSKETE".
In English (as it appeared in the article by M. Sakellariou) an Athenian asks "sledfish, what do you mean?" and a Macedonian replies "wha ye Attics ca' a hammer-fush, ma freen" i.e. in my own words, which I hope do not change the meaning of this phrase "what you Attics call a hammer-fush, (we call a) freen".
One can appreciate the value of the Macedonian's reply for the object under discussion if he does not forget that as is clear from many passages in Aristophanes the attic comedians made their non-Greeks speak broken Greek with an a mixture of barbarian words (some of them imaginary) while Lacedaemonians, Boeotians, Macedonians and other Greeks spoke their own dialects. The Macedonian's reply is in good Greek with dialect (ymmes, sfyraina) and archaizing elements (kiklhskete). Both YMMES and SFYRAINA are not attic words but they are Greek. Therefore claims that Athenians "hellenized" Macedonians seem to be baseless. It is also noted that these words were used by the Macedonians some time in the 5th century BC that is at least 50 years before their alleged hellenization.
An ambassador from Macedonia speaking to the Aetolians in 200BC observed that the Macedonians, the Aetolians and the Arkanians all spoke the same language.
The expressions "aneboa MAKEDONISTI", "MAKEDONISTI th fvnh" have been taken by opponents of the thesis that the Macedonians were Greeks as indicating that their language differed from Greek. One can claim that these formulation indicate a Greek dialect (cf [In Greek] "aiolizein th fvnh", "attikizei", "attikisti", "boivtiazein","dvrizein" etc).
To those who are more interested in the characteristics of the dialect of Greek spoken by the Macedonians the article by M. Sakellariou in "Macedonia: 4000 years of Greek history and civilization" is available on request. In general few words of non-greek origin were used in the Macedonian dialect of greek an most of these words were proper names. Some of them were names of Egyptian deities worshipped in Macedonia after the 3rd century BC. Even in the times of Herodotos (II 153, III 27, IV 155, VI 27) barbarian (non-greek) names were in use by Greeks. Strabo VII 7,1 (C321) also mentioned various names of non-greek origin such as KEKROPS (Greek: KEKROC) KODROS, AIKLOS (Gk: A.I.KLOS), KOTHOS (Gk: KOUOS), DRYMAS (Gk: DRYMAS) KRINAKOS (Gk: KRINAKOS).
It should also be mentioned that many place-names in ancient Macedonia (and modern-day Macedonia of Greece) are of Greek origin and of use in other areas of Greece as well. Such names are: Argos (Gk: ARGOS), also found in Thessaly and Peloponnesos. Arnissa(Gk: ARNISSA) reminds of Arnen (Gk: ARNHN) of Thessaly and Boeotia. Arethoussa (Gk: AREUOYSSA) also found in Ithaca, Boeotia, Syracuses. Prasias a lake and a city name is also found in Athens as PRASIAI, and many other ones (such as Oedomenae, Petra, Fila, Gortynia, Pynda etc).
Many other words of the Macedonian dialect are of ancient Doric origin such as [the Macedonian Doric and attic equivalent names are shown in Greek only]: santoria = svthria, zereuron = bereuron, barauron xarvn = xairvn arkon = argos dvraj = uvraj danon = uanon , uanatos kadaron = kauaron sarisa = dory (from the verb sairv, sarvnv) etc. Some other words of the Macedonian dialect of greek can be traced back in the Homeric poems: amalos = apalos indea = meshmbrian ( indion hmar) leykanih = laimos lisson = omalon , leion (lygos = rabdos).
Fore more details see the work of Geyer Fr., where he showed that the names of Macedonian months and festivities although they could not be found anywhere in classic Greece were archaic Greek ones and showed the Doric origin of the Macedonians.
The fact that Macedonians participated in various celebrations like the Amphictyonies and the Phocica also show the belief of themselves and the other Greeks in their origin. It is for these reasons that Professor F. Papazoglou in "Historija Hellenizma", Belgrade, 1967 claimed that Macedonians were Greeks, a claim also supported by Heinz Kreissing in "Povijest Hellenizma", Zagreb, 1988.
Prof. Arnold Toynbee in "The Greeks and their Heritages", Oxford University Press, 1981 also claimed that ancient Macedonians were Greeks.
Post-Vergina evidence.
The excavations in Vergina have brought to light many tombs that buried ancient Macedonians. There are inscription on these tombs with the names of the deceased person and those of his/her progenitors. All names found so far have been Greek. Given that some of these tombs are dated from the 350BC era, one can conclude that by some time in late 5th century Macedonians have been naming their children with Greek names. And since contacts with the Athenians were rare to non-existent at that time one can safely conclude that claims that Macedonians were not Greeks and were only 'hellenized' in the 4th century BC are false.
Published information on the excavations in Vergina is mostly in the form of papers submitted to various conferences.

What did ancient Greek writers write about Macedonia?

Aeschylus (Iketidai, 250) and Herodotus (V 22) believed that Macedonians were Dorian Greeks. Herodotus claimed that the Macedonians (called at that time Makednoi) who moved to Peloponnesos from Doris were later called Dorians.
[The English translation of the works by Herodotus we use is due to A. D. Godley and published by Harvard University Press in the US, and Willian Heineman Ltd in Great Britain as part of the Loeb Classical Library]
In Herodotus Book I, 56 (page 53) it is mentioned
"These races, Ionian and Dorian, were the foremost in ancient time, the first a Pelasgian and the second an Hellenic people. The Pelasgian stock has never yet left its habitation, the Hellenic has wandered often and afar. For in the days of king Deucalion it inhabited the land of Phthia, then in the time of Dorus son of Hellen the country called Histiaean, under Ossa and Olympus; driven by the Cadmeans from this Histiaean country it settled about Pindus in the parts called Macednian; thence again it migrated to Dryopia, and at last came from Dryopia to Peloponnesos, where it took the name of Dorian".
Elsewhere, VIII-43 (referring to the naval battle in Salamis) Herodotus wrote
"The Peloponnesians that were with the fleet were, firstly, the Lacedaemonians, with sixteen ships, and the Corinthians with the same number of ships as at Atemisium; the Sicyonians furnished fifteen, the Epidaurians ten, the Troezinians five, the people of Hermione three; all these, except the people of Hermione were of Dorian and Macedonian stock, and had last come from Erineus and Pindus and the Dryopian region. The people of Hermione are Dryopians, driven by Hercules and the Malians from the country now called Doris.".
In another passage Herodotus described how the Macedonian state had been founded (VIII,136-138).
There is one passage in Thucydides that descries the Molossians and other Epeirotian tribes among the 'barbarians'. It was proved following the excavations in Epeiros in 1950-1960 that the Molossians and other Epeirotian tribes were Greek, speaking Greek, and writing in Greek well before Thucydides' time. Thus Thucydides was wrong for these tribes. He was also wrong if he claimed, as some translators allege, that Macedonians had not been a greek tribe. Thucydides had also accused the Eurytanes, another Greek tribe, of being barbarians for their bad and improper use of the greek language and their aboriginal customs. The misinterpreted passage of Thucydides is given below. In Thucydides IV,124,1 (Loeb edition by C.F. Smith) the following passage appeared. "The total Hellenic force was about three thousand; the cavalry that went with them, Macedonians and Chalcidians, were all told a little less than one thousand, and there was besides a great multitude of barbarians".
[In Gk: "MAKEDONVN JYN XALKIDEYSIN OLIGVN ES XILIOYS, KAI ALLOS OMILOS TVN BARBARVN POLYS"]
This passage is sometimes misinterpreted so that Macedonians and Chalcidians for that matter appear to be considered barbarians by Thucydides. That this is not so can follow from an analysis of this passage. First, no one ever considered the Chalcidians, whose number is added to that of Macedonians, barbarians. Second, Thucydides distinguishes Macedonians and Chalcidians on the one hand and barbarians on the other by using the adjective few (Gk: OLIGVN) for the former and many for the latter (Gk:POLY). These two adjective clearly indicate a contradistinction.
Euripides lived many years and died in Macedonia. Many of his tragedies were written and played while he was in Macedonia. This would have been impossible, had the Macedonians been 'barbarians' (non-Greek). This is because in one of these tragedies, 'Iphigeneia in Aulis', the Greek superiority over the barbarians is emphasized. The following epigram in memory of Euripides which is attributed by some authors to Thucydides may give us more light to the actual beliefs of the people of that time (and possibly Thucydides)
"MNHMA MEN ELLAS APAS' EYRIPIDOU, OSTEA D' ISXEI GH MAKEDVN, H GAR DEJATO TERMA BIOU".
In brief, Macedonia, the land that holds the bones of Euripides is considered part of Greece.
Polyvios (VII 11,4, V 103,9, XVIII, XXXiV 7,13 , VII 9,1 IX 37,7) clearly stated his belief that Macedonia was greek, part of Greece, and considered Achaeans and Macedonians of the same race. The same beliefs were shared by Strabo as well as Titus Livius, to name a few other writers. It is also interesting to note that Polyvios describing the Balkan Peninsula he says that it includes Greece, Illyria and Thrace. One can thus deduce that he includes Macedonia in Greece. Had he not done so, he could have listed her separately.
Plutarchos(Flam. XI) describes Titus Contus Flamininus during the Isthmia celebrations claimed that Macedonia prevented barbarian attacks against Southern Greece.
Arrhianos' work is full of references to "Macedonia and the other Greece".

What is the meaning of the word 'Macedon'? References.

What is the meaning of the word 'Macedon'? References.
The word Macedon (Gk: Makedvn) is very likely to come from the Greek word 'makednos' first mentioned in Homer's Odyssey (Od. H106), and later by Herodotus, who called 'Makednon eunos' the various Doric tribes among which he included the Macedonians (Her. I.56, VIII.43).
The word 'Makednos' has the meaning of long, tall, and highlander. Some archaeologists believe that the Macedonians were called so because they were tall. Nowadays the meaning of 'highlander' is more prevalent. This is because Macedonians used to live early in prehistoric times in the mountains of Vermio in Greece.
The Greek words Macetia (Gk: MAKETIA) and Macetae (Gk: MAKETAI) were also used in early times to identify Macedonia and the Macedonians.
The biblical Hettieim or Kitim and Kitiaioi originate from Maketia and Maketai.
Hesiod in Theogonia, written in the middles of 8th century BC, claimed that Makednos and Magnes who used to live in the lands around mountain Olympus and Pieria were sons of Zeus and Thyias, daughter of Deukalion. This suggests that the other Greeks of that time believed that the Macedonians and Magnetes belonged to the same tribe (a Hellenic one).
Hellanikos, who lived at the time of Herodotus, considered Macedon son of Aeolos. Apollodoros considered Macedon son of Lykaon and thus grandson of the king of Argos Pelasgos and Lykaon king of Arcadians whose 50 sons became leaders of various greek tribes. On the other hand Aelianos considered Lykaon, King of Emathia and Pindos, son of Macedon.
Aeschylus, in Iketidai, had the king of Argos Pelasgos boasting that his family was ruling the lands beyond Pindos and Dodoni up to river Strymon (that is including Macedonia, the one part of modern day Greece).