A friend who has been trying it out, Gabriella Coleman, says it's already stable and being used by non-profits and activist collectives around the world. It has recently received an infusion of funding to polish usability. And it's under the Affero GPL!
Crabgrass: free software collaboration for distributed groups
I've been waiting for Crabgrass for years. I want to set up tasks and keep track of what my mates are doing without struggling with Gantt charts and all those tools for MBAs; looking at the grid of lines on a spreadsheet makes me think of jail. Crabgrass offers all the elements of social networking that are actually useful.