If such is not present in the internet, just give me .po specifications and requirements, I can start to create opensource php based vlc oriented (own) translation tool.
There are some such things on Internet, for example the
Narro project (an open source project, based on Drupal as far as I know).
You can get an idea
here about how it looks like (in this case the pages are in Romanian language, for Romanian translation).
While I recognize the advantages of a team work on a given translation, what I (personally) really miss is an off-line collaborative tool, that can deal with different translation stages (flags like "not translated", "imported", "complete", "locked", "in process", or something), this in addition to administrative rights (validation).
Basically, the good part with using poEdit is that there is one manager for each language and this helps to keep coherency.
This can be achieved also with collaborative tools, if the translation maintainer/manager has some reviewing/validation rights (and also possibilities to do this).
Cristi
... I think it's too hard to think