E.W.F. is correct, except that (as my historical knowledge goes) it is not provable that he was indeed a "Morgan". Some suggest that his Christian name was Morgan, but that may be somewhat un-substantiated. (Some patriotic Scots as I bet E.W.F. is...tend to suggest that as a fait-accompli) and it's POSSIBLE....but, the strength of the argument lies in some possibly dubious transliterations of now archaic Gaelic words. He was born in Briton...but it's something of some wishful thinking to say that he was provably a "Morgan". He was trained in the law and Philosophy and was only ever a "monk" in terms of his attachment to the "Church".
The differences between Arminius and Pelagius are both signifigant and insignifigant at the same time.
Pelagius wasn't a "Pelagian" as the Theological moniker goes. The term is better derived from the writings of some who are his real or alleged disciples such as John Cassian.
I have all of the available extant writings of Pelagius himself, and although debatable, they are anything but heretical or un-orthodox. So-called "Pelagians" who are some of those "disciples" of his, departed rather drastically from the Scriptures and believed what Pelagius himself clearly did not. Pelagius suffered from something of a "guilt by association" from linking him to some rather un-Scriptural and heretical remarks from some of his alleged "followers".
Pelagius was proclaimed (with a bribe of 80 Numidian Stallions from a personal friend of Augustine's and in abstentia) a "heretic" for extolling beliefs which were more the work of "disciples" of his, and not he himself.
In common fashion, most of his glorious literature was (naturally) burnt, except of course for his "Letter to Demetrius" which survived only because his followers were ingenious enough to falsely ascribe it to Jerome and not him. (Naturally, his detractors were too stupid to figure out the trick). But some of his other work has survived. European Theologians have done an excellent job in the last 80-100 years of finding and translating his remaining extant works. But they are expensive to purchase since they are not quickly translated into English. French, German, Swiss and Dutch translations are easily available from his original Latin, but the English translations are slow in coming and expensive.
They are insightful, since there is an historical context which any Patristic father can provide, but he isn't very "Theological" or very "DEEP", in his writings.
They are normative, and sometimes quite insightful, and very straight-forward. His commentary on Romans is quite charming if rather simplistic. All he does is take the passages line by line and describe the obvious meanings. Usually, he doesn't say anything you couldn't figure out for yourself.
The only correlation though between Pelagius and Arminius is that "Pelagius" was deemed a "heretic" by a Pagan and worthless Satanic Catholic Church, and thus it is convenient to create the term "Pelagian" as a by-word with which to demonize anyone who is not a 5-point Calvie.
Outside of that...there is no particular correlation whatsoever. Arminius was no doubt FAR closer to a "Calvinistic" Theology than Pelagius was, as he was taught by that system and didn't diverge very far from it.
Pelagius himself was shackled by NONE of those conventions and thus he was both a "dear friend and brother" and an abominable "heretic" in the eyes of the Prostitution-fetishist and persecution-enthusiast Augustine all in one lifetime.
