AxoSoft provide a proprietary bug / issue tracking system which they licence in various forms. As a hosted solution, a licenced application, etc.
The goal of the Subversion project is to build a version control system that is a compelling replacement for CVS in the open source community. The software is released under an Apache/BSD-style open source license.
This is the online home of Version Control with Subversion, a free book about Subversion, a new version control system designed to supplant CVS.