Cool first Ruby project, for sure, but "Dropbox clone" is a stretch. That phrase does help explain the idea in a nutshell, but this is essentially a script that polls at intervals and either pulls from the remote repository, or adds, commits, and pushes from the local one.

Incidentally, when I read the source I didn't notice any conflict handling, so you might want to be careful if you intend on using it for anything where conflicts are a possibility.