In theory, sure. Crypton.io itself is available on github and you could build your own server.

On the Encryptr app side, src/app.js uses window.crypton.host and _.port to specify the crypton endopint to connect to. I think the app store build of encryptr uses a crypton endopint at devgeeks.org.

You could just use (apache) cordova to roll your own build of the android app with app.js set to point to your preferred self-hosted endpoint.

YMMV.

Note: this is definitely a product at the MVP stage. The platform is capable of implementing data sharing, but that is not currently used by the Encryptr application.