Welcome to the ownnote wiki!
Take note (lol!) that this is the server-side OwnCloud app OC/OwnNote. The source code of the matching client on the Google Store that is referenced is https://play.google.com/store/apps/details?id=com.nowsci.ownnote.
This is worth mentioning, because there are other projects with confusingly similar names, i.e. an OwnCloud app OC/Notes (https://github.com/owncloud/notes) with an Android client called MyOwnNotes (https://github.com/aykit/MyOwnNotes). These are (currently?) not compatible with this project!