As long as the game requires TATW as base, it's a submod and technically permitted. If not, I'm confident ModDB rules do not accept blantant use of other mod's content without permissions either.
That said, it's unclear what skills he has to begin with (or if there's any actual comptenet team to begin with), large project ideas tend to die in 99% of the cases because founders failing to understand the workload required, and leaders do not get modders to join without proof of own competence in the first place.
The references to lionheart and 'apollo, while great Youtube:ers (I follow them both), do not have any relevans to this matter.