Thanks for the Module::Build hint. I was deeply scarred some time ago by Module::Build :), but I know it's moving fast and I'll have to investigate it more.
Your point about team communication is a good one, but perhaps orthogonal to Taskcard's focus. Taskcard is clearly overkill for an experienced team doing full-on XP in a single room. I believe that's only a fraction of the people using some elements of XP, and an even smaller fraction of those who could benefit from a centralized task repository.
If you're trying to manage 5 volunteers on an OSS project, each in different time zones and each with only a few hours to spare each week, I think Taskcard could be really valuable. There's some feature work to do, but much interface design: when it's ready, it'll look simpler and do more.
Thanks for your long and useful reply.