For more info: http://blog.kowalczyk.info/software/fofou/
Fofou (Forums For You) is a simple forum software inspired by Joel On Software forum software (http://discuss.joelonsoftware.com/?joel).
It's mostly a port of FruitShow PHP forum (http://sourceforge.net/projects/fruitshow).
This is a version for App Engine, written in Python. I no longer work on it.
There's another version written in Go: https://github.com/kjk/fofou
For Google App Engine version you need to get App Engine account and upload fofou (see http://code.google.com/appengine/docs/gettingstarted/uploading.html for details).
Once installed, you can create one or more forums through web interface.
You'll quickly see that Fofou differs in many ways from most common forum software. There are good reasons for the differences and Joel Spolsky describes those reason in great detail: http://www.joelonsoftware.com/articles/BuildingCommunitieswithSo.html
The code is written completely by me and is in Public Domain.
Html/css/js files are mostly lifted from FuitShow, so they fall under FruitShow's BSD license.