Technically speaking the GPL doesn't force companies to "give back". It simply says you must give the source to anyone who's been provided a binary. Not even by

Technically speaking the GPL doesn't force companies to "give back". It simply says you must give the source to anyone who's been provided a binary. Not even by default, you can comply by making them ask and mailing them physical media (if you really want to be a jerk about it). A vast majority of the GPL "giving back" I see is Company XYZ dropping a messy tarball in some obscure portion of their web site. The code never goes anywhere, and frequently not upstream. No one else benefits from their work or GPL compliance. Not that this is a good approach - the real companies that "get it" know they're better off upstreaming anything they want/need to depend on in the future.