GPL Edutainment Software

haxot writes: "I'm the technologist at a local library. In our lab, I've managed to get some recognition for tools such as GIMP and Open Office, and even such toys as Bomberman & BZFlag. Now I'm turning towards the children's computers, which are mostly filled with ancient, buggy, rather boring games that try to be interactive TV shows rather than something entertaining. I'm looking for (preferably multi-platform — I want to be ready for an OS switch to Linux) OSS style software, not picky about the license; but most especially picky about the software actually having that "neat" appeal. Some stuff I've found already is Gcompris and Tux Paint
My focus is the 2 year old to 8 year old — but I'm happy to hear teen-oriented suggestions too. As a public library however, I can't have any software on the computers that is risqué, gory, or too violent.
So does anyone know of any family-friendly edutainment, multi-OS OSS games?"