ZEZeroGravitas·Jun 2, 2022
Various old skool text adventure games are open source (-ish, in some cases).
If you are already experienced with them then "Counterfeit Monkey" takes it to the next level with a great twist based on anagram-like magic/technology for turning objects into other things by adding/removing letters from their name:
> Anglophone Atlantis has been an independent nation since an April day in 1822, when a well-aimed shot from their depluralizing cannon reduced the British colonizing fleet to one ship.
> Since then, Atlantis has been the world's greatest center for linguistic manipulation, designing letter inserters, word synthesizers, the diminutive affixer, and a host of other tools for converting one thing to another. Inventors worldwide pay heavily for that technology, which is where a smuggler and industrial espionage agent such as yourself ca
Read the rest
n really clean up.
> Unfortunately, the Bureau of Orthography has taken a serious interest in your activities lately. Your face has been recorded and your cover is blown.
> Your remaining assets: about eight more hours of a national holiday that's spreading the police thin; the most inconvenient damn disguise you've ever worn in your life; and one full-alphabet letter remover.
> Good luck getting off the island.
https://ifdb.org/viewgame?id=aearuuxv83plclpl
https://github.com/i7/counterfeit-monkey
If you're new to the genre then "Lost Pig" is a good place to start, though technically it's licence (Creative Commons Attribution-NonCommercial-NoDerivs 3.0) is not open source.