Finally people realize that Dropbox is unethical. They've been denying your computing freedom for years now, but it took hiring Condoleezza Rice for people to start to catch on.
I was looking at their site for a while and I really have no idea what they sell. I'm sure it's just a communication issue, but it seems kind of weird. Like I have to register to find out that I will get a client for free but pay $10K/month for the enterprise software or something.
How do they make money? Apparently you use your own server so you must buy the code?
ownCloud is free/open source software - you have no obligation to use ownCloud's servers or pay them anything - you can download both the client and server source code, host the server on your own machine, and connect to that with the client.
ownCloud run a business where they can host a copy of the server software for you, if you don't have your own machine or a usable connection - but there's no requirement to use that - you could spin up an instance in Amazon's cloud or elsewhere too.
ownCloud is free software licensed under the AGPL. This means that you can run the software on one of your own machines or find a hosting provider. The company behind ownCloud offers enterprise installations, which is probably what confused you.
Personally, I haven't gotten around to self-hosting yet and use a small free account at https://owndrive.com/
Replace dropbox with ownCloud. http://owncloud.org/