I want to set up a sync repositiory that would be similar to Dropbox.

Goals/Requirements:

1. Free (Open Source very preferable)
2. Linux host (probably Ubuntu)
3. Windows/Mac/Linux clients
4. Potential for multiple users with limited access (optional)
5. Preferable easy, doesn't necessarily need to be automatic
6. Revision control very preferable

Basically, I want to be able to use multiple computers, possible with different OS's, and be able to access, use, and sync files across all of them. I also want to have a local copy of the repository for when I'm not connected to the network (as if I'm working on a laptop, I want to keep a local repository to keep revision and merge later with "master" repository).

For example, I'm editing a few pictures on my laptop during the day outside of my network, but when I get home, I would like to sync the changes, including incremental changes, with my desktop at home.

I would also like my roommates to be able to access and use this repository too but limit access to certain files. For example, I may want to use this to backup financial records but wouldn't want them to have access to those files.

I'm a programmer and familiar with SVN but I know that wouldn't be the most appropriate since it doesn't handle binaries well and doesn't keep a local repository. I know better choices exist but I don't really know them well enough to choose the best one.