Search 'HandmadeHero' on GitHub. There's like 10+ repos publicly accessible already.
Legally, if you stumble across someone else's public repo, read their transcribed code of Caseys' lessons not realising the original source is not public domain, would you be ok?
I think some of those 10+ repo don't even mention Casey or what the code is for. Affectively everything Casey's doing is just floating out their in the public domain.
UPDATE: The most up-to-date public repo appears to be
https://github.com/RyanRothweiler/HandmadeHero, which at time of this post is at Day 33