This question came up and during a discussion, it came up that it wasn't exactly 5e that was being played.
The game itself is Heroes and Dragons with more specific rules found here. Fundamentally, it seems based off of D&D 5e's SRD (translated into French), but has been expanded and is it's own thing.
I'm fairly certain that because it's based on the 5e SRD this is legal and fine, but I want to verify that as well as determine which system the question should be tagged with.
It currently is tagged with 5e as that is the 'core' system, but it's not the system itself.
What I'm asking is:
Should we tag to 5e because that's what OP is asking us to use in determining homebrew balance? Or should we tag to the actual game?
Can we tag/link to this as a legal game?