Thanks for your replies, all completely frakin useless as expected. I was very clear in the OP what I was looking for. Of course I have researched this and have sampled
JIRA
Trac
TestLink
Bugzilla
Eventum
In your fit of genius, you forgot to tell us anything about what else you'd done, and for legal reasons I'm no longer allowed to use my psychic powers.
All you did was ask for OS SDLC tools, and when you got an answer, had a bit of a hissy fit. Good work