The Data Analysis and Report Toolkit (DART) is a truly Open Source, feature-rich student information system (SIS) software package. In short, it is written in PHP, and runs on any web server with the free software combination of Linux, Apache, MySQL and PHP (LAMP). DART is therefore free like a puppy! You can take it home with you, but care and feeding is something you must provide on your own, or contract with others to do for you.
The GitHub site is: https://github.com/dartproject/DART
We have a Google Group: http://groups.google.com/group/dart-project/ And, there is access to our live DART development demo site here: http://wiki.bssd.org/index.php/DART_System
We are using MediaWiki 1.16 on our servers currently. Dokuwiki is also a great alternative that does not require a MySQL server to run and operates well on multiple platforms.