That’s one of the things I love about Automattic – freedom and community-driven development:
In this spirit, we are announcing today that all of the official Simplenote client apps are now Open Source Software under the GPLv2 license. In addition to the previously open sourced Electron app, you’ll now find the source code for the iOS, Android, and macOS applications on our GitHub page.
As an avid notes keeper, I’ve been using Evernote, Mou, MacDown, and eventually ended up with Simplenote. Sync’ed on every device, minimal markup, clean tagging – exactly what I looked for.