GitHub qua "template engine website" is "NOT permitted". That's certain.
GitHub qua code host? Not only is that, in fact, not stated "in no uncertain terms", but insisting that it's both forbidden and that it's clear that it's forbidden comes across as trying to will your way to truth.
You are not permitted to use sites that generate HTML, period. Even if you use a "site that generates HTML" like Github only as a file repository, that is still against the rule.
Your argument would be fair if the rule read like "using sites, such as Github, to generate HTML are not permitted", but that is not what the rule says.
I am not quibbling about whether the no-GitHub-whatsoever interpretation is an unreasonable interpretation of what's in the rules. I am specifically raising the issue of the hyperbolic and inappropriate use of the phrase "in no uncertain terms" in what you wrote.
GitHub qua "template engine website" is "NOT permitted". That's certain.
GitHub qua code host? Not only is that, in fact, not stated "in no uncertain terms", but insisting that it's both forbidden and that it's clear that it's forbidden comes across as trying to will your way to truth.