I think a system such as WordBee (
http://www.wordbee.com) is more appropriate for such multiuser system. I believe a couple of years ago someone modified a Project Manage System for programmers to do translation. That way you have a responsible leader who can control access and rollbackward or forward anything that was done, such as the distributed revision control and source code
management systems used by open source programmers.
For single users, SDL Trados is the dominant software for translation...