Correct. Kroc has removed his GitHub repositories, see this note: https://oldbytes.space/@Kroc/116975832359762668
Kroc still has code shared through Codeberg. You can find the code repository here: https://codeberg.org/Kroc/NoNonsenseForum
A download-as-ZIP is also available there, just like how it was with GitHub. Try https://codeberg.org/Kroc/NoNonsenseForum/archive/master.zip