Comment Re:Opensource and [MS-PL]? (Score 3, Insightful) 140
GPL-compatible does not mean that you can simply copy and paste code willy-nilly into a GPL project.
Most BSD style licenses are unencumbered enough that you can relicense direct derivatives (not just composite works) under practically any terms you want. Commercial companies do this all the time, and it is in fact what makes BSD style licensing for open source software projects so controversial - anyone can create a proprietary fork at will, with components that quickly lose their BSD character as modifications are added.
GPL licensed derivatives of BSD licensed components can be created in the same manner. It is the copyright of the authors of the modifications that makes the relicensing have teeth, it is the lack of a prohibition on additional license terms in BSD style licenses that makes it possible.
The MS-PL, on the other hand, specifically prohibits this practice, much like the Mozilla Public License (MPL). Both are moderate copyleft licenses, designed to make sure that derivatives of covered source files are always available under the terms of the original license.