See here. Now if, for example, we wanted to make Chandler collections available as GData calendar feeds we could do so without worrying that Google's lawyers might come after us for infringing on their patents. This, of course, begs the question of what patents Google has filed related to GData, and I'm not sure I know the first step in finding out, though I'd guess it would be through the US patent office.

Incidentally, implementing GData Calendar and possibly notebook feeds in Cosmo would be a fantastic project for Summer of Code students or anyone interested in getting involved with the project, and I've updated this page accordingly.