Open Source Software Project Management Web Service?

Wow, the title “Open Source Software Project Management Web Service?” is a mouthful.

Working on a small project with a friend (mentioned in “Learning by doing something else“) is a great opportunity to check out tools in other parts of the web development stack. I’ve been interested in trying out some of the software project management services and software.

(At Automattic, we mostly use prologue and trac. This is a fantastic combination!)

Likely the best approach for this project would be to first identify our needs and wants and then work through the available web services to find the closest matches.

After it being a web service, the next big want is for it to be open source software.

I have not yet been able to find any software project management web service that is open source software. Any hints?