They are not misunderstood references to "other gospels." They are real references in the Bible.
In Galatians 1:6-8 (KJV) Paul writes
6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
These other preachers taught "another gospel" which Paul calls a perversion and therefore not really a gospel at all. But it was presented to the Galations as "gospel."
Later in the same letter he writes (Galatians 5:11 (RSV)) ... "But if I, brethren, still preach circumcision, why am I still persecuted?" He is refering to an earlier period in his life when he preached the gospel that many of the apostles (especially James) preached - that the gospel required gentile males to be circumsised and become jews. Paul seems to have required Timothy to be circumcised, but he had understood that God's grace did not require circumcision by the time Titus became a believer. He had to battle hard to get this accepted by the elders in Jerusalem, but eventually did. It was partly through this process, that Christianity moved from being a jewish sect to becoming a distinct faith. But for many years the gospel preached out of Jerusalem included the necessity of circumcision. Note also in early Acts, that the disciples continued going to the temple to worship and teach.
If you read Peter's Pentecost message you will see that he retained his very Jewish idea of the Messiah. The crucifixion was from their perspective something that shouldn't have happened, and which had to be corrected by God in the resurrection. Furthermore, they believed Jesus was returning soon (certainly before the death of John) and so the message contains a warning and an implied threat: if you don't repent (of crucifying Jesus) you're facing his wrath when he returns (and that soon) to impose his rule. There is nothing here that sounds like "Jesus died for our sins," which Paul later preached and refered to as "my gospel."
Some of the disciples had been followers of John the baptist who preached confession and baptism for the forgiveness of sins. Later we read of Apollos, another follower of John the Baptist from Alexandria (Egypt), who apparently went abroad and preached what John taught, including John's view of Jesus. In Acts 18: 24-26 we find the account: "Now a Jew named Apollos, a native of Alexandria, came to Ephesus. He was an eloquent man, well versed in the scriptures (i.e. the OT). He had been instructed in the way of the Lord; and being fervent in spirit, he spoke and taught accurately the things concerning Jesus, though he knew only the baptism of John (i.e. nothing about the baptism of the spirit so he might even have missed the whole crucifixoin and resurrection because it was both immediately before and after that Jesus promised the spirit). He began to speak boldly in the synagogue; but when Priscilla and Aq′uila heard him, they took him and expounded to him the way of God more accurately." In other words he wasn't teaching and preaching accurately. (By the way did you know there are still followers of John the Baptist?)
You could say that Peter preached a Power or Crown gospel, very similar to "hell fire preaching" while Paul came to preach a Love or Cross Gospel. But that wasn't until he realised that the cross was not a mistake that God had to correct, but the whole point of Jesus coming - to die for our sins. Previously he had been preaching the messianic gospel based on the 'traditional' Jewish interpretation of the OT. When he got his vision (probably between Athens and Corinth) he was shaken to his Jewish core - and saw immediately that it would be "a stumbling block to the Jews" (who could not possibly accept that their Messiah could/would be crucified by gentiles) and "foolishness to the gentiles" who would think it was idiocy that you could win by submitting, live by dying. This guy who up to that moment was fearless in face of stonings, whippings, mobs, and being run out of town by jealous religious leaders, or prepared to face that age's academia and cynics (at Athens) suddenly became totally silent for several days, until he was specifically told by the Lord not to be afraid ---"for I have many people in this city." Ultimately the other apostles came round to understand and accept this gospel, and that "you are saved by faith" not by works.
The New Testament shows a lot of the development of what we think of as the "gospel" today but it wasn't so from the beginning.
There are clear indications that there were divisions following the interpretations or personalities of different people:
1 Corinthians 1:11-13 (RSV)
For it has been reported to me by Chloe’s people that there is quarreling among you, my brethren. What I mean is that each one of you says, “I belong to Paul,” or “I belong to Apol′los,” or “I belong to Cephas,” or “I belong to Christ.” Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?
