One of the 2010 objectives is community localization:

http://wiki.maemo.org/Objective:Community_localization

The goal is to allow the organization of translators in language teams in order to produce community supported languages for Maemo. This would include the official releases and the tool could be open to community/third party applications as well.

After some research and thoughts, I think we could have a look to http://transifex.org/ an open source tool created precisely for this kind of purpose. It is being used by the Fedora project: http://translate.fedoraproject.org/

A strong candidate would be also https://translations.launchpad.net/ - planned to be open source later this year. A drawback seems to be (please correct me if I'm wrong) that Rosetta is part of the whole Launchpad infrastructure and it's not easy to detach.