It made me curious, so I looked at their TOS[1], and they seem somewhat permissive about things like this. Though vague about where/when you cross the line.
Like, this seems clear:
"should not be used for...any other activity unrelated to the production, testing, deployment, or publication of the software project associated with the repository where GitHub Actions are used."
But then:
"but a low benefit Action could be ok if it’s also low burden"
[1] https://docs.github.com/en/github/site-policy/github-terms-f...