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

Hi there! Yes, I will switch to a more distinctive icon in the future once I can afford to hire a new designer.

Multiplayer was quoting the correct reason. I also exeplained more about the timeline here: https://github.com/nuttyartist/notes/issues/690#issuecomment...

Tldr: The FOSS version earned a stable revenue through Google Ads placed on the website, since the website ranked high on Google searches. Two years ago, that changed since the website got de-ranked, so I created a different, proprietary version of the app based on the FOSS version but with a totally revamped block editor that I wrote from scratch - that I worked on full-time for a whole 1 year.