OK, looks like the Kanban board is the pet we like. On Github, the board can be made of (classic) issues and notes. I believe notes are enough as replies to this thread don't suggest we need anything special from issues. (Still, they can be mixed so there's no… issue.)
Anyway, shall I go and create a "project" for the great Sabayon <heck, how will it be called?> release that is in the works?