Useful Offshoots
Oh rad, it looks like open-sourcing Sproutliner resulted in something mo'better - iOutliner. It seems to add the two most requested features - user logins and project groups (the third, in case you were wondering, was a 'textarea' field type).
Apologies to the iOutliner guys for the pain they must've suffered in having to deal with the must-finish-it-in-a-day-bah-who-cares-about-correctness Sproutliner code.