Here's a suggestion that will surely rankle some in the free software/GPL community, but which might be of good benefit to the overall success of such systems.
What I propose is a GPL-like licence under which source code could be published, but which forbids effectively one thing: Work to make it run on proprietary operating systems, in particular Windows and MacOS.
The goal would be to allow the developers of popular programs for Windows, in particular, to release their code and allow the FOSS community to generate free versions which can run on Linux, *BSD and the like. Such companies would do this after deciding that there isn't enough market on those platforms to justify a commercial venture in the area. Rather than, as Richard Stallman would say, "hoarding" their code, they could release it in this fashion. However, they would not fear they were doing much damage to their market on Windows. They would have to accept that they were disclosing their source code to their competitors and customers, and some companies fear that and will never do this. But some would, and in fact some already have, even without extra licence protection.
An alternate step would be to release it specifically so the community and make sure the program runs under WINE, the Windows API platform for Linux and others. Many windows programs already run under WINE, but almost all of them have little quirks and problems. If the programs are really popular, the WINE team patches WINE to deal with them, but it would be much nicer if the real program just got better behaved. In this case, the licence would have some rather unusual terms, in that people would have to produce versions and EXEs that run only under WINE -- they would not run on native Windows. They could do this by inserting calls to check if they are running on WINE and aborting, or they could do something more complex like make use of some specific APIs added to WINE that are not found in Windows. Of course, coders could readily remove these changes and make binaries that run on Windows natively, but coders can also just pirate the raw Windows binaries -- both would be violations of copyright, and the latter is probably easier to do.