Lurking in a dry, legalistic and apparently quite specific page on the Drupal website, is the commendable result of a lot of hard work, both from the the Software Freedom Law Center and from the Drupal community.
Drupal.org have produced a Licensing FAQ to explain some of the subtler aspects of licensing under the GPL. The questions themselves are Drupal-oriented, but the FAQ itself has been prepared by the SFLC, an independent body, so the answers are broader than that.
I've noticed from the slightly confused sidelines that Drupalers have been niggling away at these issues for ages. Their heated exchanges and occasional quarrels are the fuel that has kept this wagon moving, and they've finally rolled it into town with a GPL-in-practice primer that's worth reading, whatever you're working on, and especially if you're integrating with web services or third-party libraries. Well done to all involved.
