Opensource alternatives for HP ALM

I'm looking for an opensource tool(preferably web-based) that would have the important features of HP Application Lifecycle Manager(ALM).

kindly suggest any such open-source tool that would serve best for my below requirements:

(1) Keeping a track of all bugs, just for reference, mainly i will be using Bugzilla for this.

(2) Keeping a track of all the constantly changing requirements.

(3) Can store all user documents and other useful documents.

(4) Planning a release, and info. about all other previous version ups.

The applications that i will be testing are generally not big, so getting a paid version of ALM is not helpful. I need to track the changing requirements, and preferably get a graphical representation of the application life-cycle till its release.

Kindly suggest any site/resources which might be helpful.

Thanks in advance.