YetAnotherNick is probably referring to the geforce eula [1] which says:
"Customer may not [...] provide commercial hosting services with the SOFTWARE. [...] The SOFTWARE is not licensed for datacenter deployment, except that blockchain processing in a datacenter is permitted."
So if you were e.g. an ad agency artist using a 4090 at your desk to generate images for commercial use - that's fine, because it's not in a datacenter, and the commercial services you're providing with it aren't hosting.
I've never heard of nvidia taking any enforcement action, or defining precisely when an office becomes a datacenter - I suspect this is mostly to ensure the big cloud providers don't offer 4090s.