Open Source document collaborative web tool

I need to solve a problem. My company uses word documents with the demands of our works, but it's getting messy.

I need a open source project that i can implant in my company that can:

1. Make different users work on the same document
2. Grant permissions for editing and/or viewing per group or specifics users
3. Store and view document revisions
4. "Who's editing/viewing"
5. Document editing interface similar to Microsoft Word
6. Export to .doc
7. Real time editing for more than 1 user in the same doc (optional, but would be good to have)
8. Chat (optional, but good)

Any ideas??