What's the licensing of these samples?

Perhaps consider CC0? https://creativecommons.org/choose/zero I think CC0 would allow them to be reused in any project no matter the license, without requiring attribution. Do others agree with that?

Regardless, best practice for a project which uses any of these samples would be to record the origin in version control, even if credit is not given in the project source code.

It's really important that sample code have clean provenance, since others will be inserting it into their own projects then possibly mutating it and making it difficult to extract. Are these samples all completely original? And will there be any IP controls as far as what you accept for Github pull requests?

(edit: don't try to use markdown for links.)