To me this illustrates that if you want to ensure that improvements to your code are shared back, you'd better use the AGPL license ( http://www.gnu.org/licenses/agpl.html ) instead of GPL. Quote from the AGPL preamble: It requires the operator of a network server to provide the source code of the modified version running there to the users of that server. Therefore, public use of a modified version, on a publicly ac…
So if you are a developer and want to see your own library and code used by corporates such as Google and many others, a more liberal license is the only way to go.
If it is a javascript library or a web application, again, a more liberal license is the way to go since the FSF insist that a script include means your entire app must be GPL.
Using copyright law to force corporations and developers to become contributors and active participants in your software project is, to me, a ridiculous notion.