wotc_logoIt only took Wizards of the Coast 7 months after deciding to revamp a GSL that angered the RPG industry to finally do it. The GSL allows you to use WotC material in order to create your own extensions that work with the material.

The new GSL [PDF] removed the contentious section concerning the old OGL. It basically lets you do what you want if you include small excerpts of unchanged content (you may extend the content) with proper legal attribution. You can’t use the GSL for products WotC considers offensive: extreme violence, nudity, sexual, racist, or offensive to any real-world people.

You can also cancel your relationship with the GSL, with time to sell off your inventory. More details here.

(source)