I just noticed that we have the (older, more well-established) ogl tag as well as the (newer, used on only two questions) open-game-license tag. I went to the ogl tag and suggested the other as a synonym, so go vote it up and make it happen!
Before debate ensues about which should actually be the tag and which the synonym: our usual policy is to use the more common term within the wider community, and "OGL" is used overwhelmingly more than the full "Open Game License", just like "D&D 4e" gives us dnd-4e because it's used overwhelmingly instead of the longer version. That seems clear enough to me that I don't think it needs discussion, but it's possible there's a flaw in that reasoning.
As a side note, the tag wiki text in open-game-license is excellent, so I replaced the tag wiki text in ogl with it. Props to @MattThomason for that text!