hi mark,
i have found insoshi a pleasure to work with because of its simplicity. however, my experience has been that because forks are often customized, it becomes non-trivial to use the pull request mechanism to share code upstream which may account for why there are so many forks and so little contributions to the original fork. if anyone is interested, i would like to have a discussion here about how to overcome this problem.
regardless, nearly two years ago, on a mutant/special purpose fork, some developers in SF and NYC contributed the code necessary for heroku support. and this past summer, i did a rails3.0 branch which has been running on a public test site since july (but hasn't gone into production for lack of testing). so, it's been done (with authlogic instead of omniauth) and you can probably save a bunch of time referencing this work or possibly even disabling the unneeded features. here is the rails3 branch:
https://github.com/oscurrency/oscurrency/commits/rails3/i'll be glad to assist if you have any questions regarding the upgrade on this branch.
cheers,
tom