Open Source is a set of principles and practices on how to write software. Literally "open source" means the  source code is available to the users.  Basically, if I tune you car with open source software the map I design for you is yours to keep and modify as you see fit.  I will even help train you to use software to log and further modify your car if necessary. This is done with not only the intent on getting the most out of your car, but educating the end user if they are interested in learning more about their own vehicles.

http://www.grimmspeed.com
GrimmSpeed - Subaru Racing Parts. We're an authorized Grimmspeed dealer.

http://forums.nasioc.com
NASIOC - One of the largest Subaru Communities     

http://openECU.org
OpenECU.org - Community resources, home of EcuFlash, a Subaru and Mitsubishi flashing utility

http://www.romrraider.com
RomRiader - Subaru logging and ECU editing software and online development.