Hello Cristian,
Kudos to Alex and you for starting the ball rolling on this project.
I recommend you to get an account in our repository [1].
Integrating this into ConfirmEdit extension shouldn't be hard. It's the
extra features what makes this tricky. This system is interesting for
gathering translations, but doesn't work for verifying that the answer
is right. How would you verify that?
The approach that comes to my mkind is to show both the current captcha
plus another, optional, captcha, with a note about how filling that
second captcha helps wikisource, and that the answer will be logged with
their username/ip.
Then dump all answers in a log restricted to captcha-reviewers.
1-
http://www.mediawiki.org/wiki/Commit_access#Requesting_commit_access