Dropbox alternative [closed]

It's pretty new, and probably not very stable yet, but you should keep an eye on SparkleShare, which - I think - is exactly what you want.

I don't normally pimp Novell products, but their OES feature 'iFolder' does exactly what you're asking for. Implement an OES and you've got what you need.

A web-based FTP interface isn't really anything like Dropbox. What makes Dropbox so nice is that users need very little interaction with it. They have a folder on their local PC that is automatically sync'd to the Dropbox cloud server. Something like iFolder might be up your alley. If you're looking to roll your own, I would look into lsync, and possibly some kind of notification system a'la Growl or inotify. The tricky part is going to be figuring out how to configure multiple user access to the same data.