Name of the software: FreeDink
Why include it?: It is a Zelda-like game with some RPG elements and people can create their own adventure using FreeDinkEdit. Since the release of the original Dink Smallwood game in 1997, people keep making mods for it to this day.
Is it open source?: Yes. FreeDink is based on the source code of the original game released in 2001.
Tarball link: https://ftp.gnu.org/gnu/freedink/freedink-108.4.tar.gz
Source repository link: https://savannah.gnu.org/projects/freedink
Note: It is also recommended to add DFArc 3 and FreeDink data. The former is a frontend which lets you run custom adventures without using a command prompt, the latter contains files required to play the game.