I was wondering about that too. This is in the article linked to https://rubymamistvalove.com/block-editor

7. The previous version of Daino Notes, called Notes is FOSS (free and open-source software) available at https://www.notes-foss.com/ and the source code is available at https://github.com/nuttyartist/notes. I decided to make Daino Notes closed source due to difficulties in monetizing FOSS. In order to comply with Notes' MPL license, all common files between Notes and Daino Notes are published in https://github.com/nuttyartist/daino-notes-public