Seafile

Client for the Seafile cloud file server and project management software. If you
are in a small team with a few people, you can create a group in Seafile and
invite other team members. Team members can then maintain file libraries
together and collaborate around them.

You can try the demo, sign up for an account at the
website, or since the server-side is also free-as-in-freedom, it can be
installed on any server and configured to work with the app.