As others have noted, as an Apache project, the CouchDB project can't be "purchased by Oracle". Obviously you meant that somewhat metaphorically (and as a reference to MySQL), but it's worth noting:

MySQL was the product of a private company. It was always possible for it to be purchased, and that eventually happened. The same is true for many modern databases, including most of the major NoSQL databases. CouchDB cannot be. Yes, there's risk of the project could die in a variety of ways, but there is an entire class of risks that CouchDB is not subject to, when most of its competitors are. If you really want to avoid having your DB purhcased and killed by Oracle, you'd actually prefer CouchDB over, eg, MongoDB.

Beyond that, you say: "You'll have to clone Couch's REST API". That's actually the other half of what makes CouchDB a safer bet: The HTTP protocol is itself open source, well documented, and has already been cloned repeatedly. It's used by quite a few different projects in different ways, including PouchDB, CouchDB, TouchDB, Hoodie.io, BigCouch, and CouchBase Lite.

If you're curious about the topic, I recommend this blog post: http://caolanmcmahon.com/posts/couchdb_is_not_a_database/

Yep. There is a reason people abstract things. Sometimes people get a new toy and just go a bit overboard, want that one tool to solve all their problems.

Don't get me wrong, CouchDB is awesome, but it isn't the answer to everything.

CouchDB can’t be bought by Oracle or anyone, since it is run as an independent Open Source project and under an organisation (the Apache Software Foundation) that allows and supports commercial entities contributing, but single vendors can never control the project in a way that a single vendor product could.

You are still vulnerable to CouchDB as a project folding, but since it is all Open Source and open discussions, that one is easy to find early on.

And finally, you could just use one of the other implementations of the CouchDB API available :)