"Vote on the OCT" = "Cast a vote in the OCT elections", yes.
Using the screenname is fine as well, but username is unique and using username allows us to gradually switch over to using user names instead of e-mails, so we have one login for CVS and openacs.org.
I like your idea of the contributions showing up on the profile page, but we should get the contributions in to a list, which is paginated and can be filtered, as otherwise it will be too long for a couple of people.
