Open Source Software

GNU Chess

https://www.gnu.org/software/chess/ 

7 open source Android apps for chess players

By Joshua Allen Holm (Alumni)June 22, 2016

https://opensource.com/life/16/6/open-source-android-apps-chess  

A curated list of free and open-source chess resources

(information: October 2022)

https://www.reddit.com/r/sharechess/comments/v5pcje/a_curated_list_of_free_and_opensource_chess/