But in form of a command shell this software controls the hardware of the Arduboy

A surprisingly fully featured little OS for this device. Features a terminal, a watch, calculator, full control over the system in all available outputs, and more. While it does lack multi-user function as for multitasking, it still gives a strong impression of “operating”.

https://github.com/zooxo/aos

https://www.youtube.com/watch?v=dVvj3j-pYlQ

https://community.arduboy.com/t/aos-arduboy-operating-system/6717

Notes text editor allows you to save text to the EEPROM

A simple but also functional clone of the Classic Mac OS desktop environment. Features a terminal, an EEPROM monitor, a remote keyboard/mouse function, and more.

https://github.com/jhhoward/Ardutosh

https://community.arduboy.com/t/ardutosh-classic-macintosh-style-desktop-environment/8298

It includes seven Apps for the moment, but can barely hold more

Self-describes as a Toy OS, but is capable of doing a few simple PDA-esque tasks, as it’s in the name. The GitHub repository appears to have been taken down, hence the archive link.

https://community.arduboy.com/t/pocket-pda-v0-8-0-a-toy-os/2869

https://web.archive.org/web/20180613071013/https://github.com/pocket-arduino/pocket_pda

This program is still a demo, there may be bugs

A miniature word processor for this little thing. Capable of editing, saving, scrolling, and using most characters.

https://github.com/GameExpress/WordMicroprocessor

https://community.arduboy.com/t/what-is-this-an-arduboy-word-processor-update-0-2/5480