Yesterday saw the release of the D&D 4e GSL and SRD. This has promoted some chatter on the Enworld forums over whether the GSL is unfair to the consumer? and a dummies guide to the GSL , which includes:
4. You can use our stuff for free, but you have to follow our rules.
4.1. You can refer to everything we list in the SRD, but you can’t redefine any terms in said SRD. You can add more stuff relating to those terms, though. We can update the SRD whenever we want. It’s up to you to make sure you’re in compliance.
4.2. You have to use our logo on your books. You can use it for other stuff too.
6. OGL stuff.
6.1. You can convert your stuff to GSL, but you can’t sell your old OGL stuff, except for your back stock. You can’t convert back ever.
6.2. You can’t weasel out of 6.1 either.
6.3. If you try, you don’t get to play anymore.