This is silly. The software FSF is most opposed to is protected not as much by copyright as by simple trade secrecy. It's not from honoring copyrights that DRM systems derive their power; that would be tautological, since the point of DRM systems is to thwart people who ignore copyright.

In a world without copyright, large corporations would have free rein to slurp up all the world's public software, extend it however they like, create whatever remaining functionality they needed, and publish none of it. None of what the GPL's copyleft attempts to accomplish would be possible.