IIRC even virtualised the OSX license requires that OSX ultimately run on apple hardware and nowhere else. You could use a colocated host rather than having a member of the team physically owning a mini though.
Because otherwise they're violating the terms of the license agreement which means at best they get no support and are 100% on the hook for anything breaking and at worst they're at risk of legal action?
Building a hackintosh in your bedroom is one thing, violating the license agreement of the tools you're using to do your job is another.