Both of those are allowed under the GPL. See http://programmers.stackexchange.com/a/61038 for the former, and the latter is allowed under just about any open source license so long as you adhere with the rest of the terms; in fact, that's the pre-GitHub definition of a "project fork". Under the GPL, others are even free to sell your software as long as they link/ship the source code (probably not what's happening in your case, but I'm mentioning that anyway for the sake of discussion).
How will this affect the future of Mayan EDMS? It is too early to tell, what is certain is that the latest technologies being added to Mayan EDMS must be protected until they are ready to be released.
I might be biased because anything I write is MIT/BSD-licensed, but I don't understand why the fact that there's a few "unauthorized" forks of your project out there is deterring you from continuing working on it. Chances are, those forks have not a single user, and even if they do, so what?