I don't feel like I can say with any certainty that any of them is definitely doing it for the money, but I don't feel like it's something that can be disproven either.
I agree that no one can prove or disprove whether Bo is just trying to cash in with ToT, all we can do is speculate, so I'll go ahead and do that...
What's the argument for Bo not caring about the money? Is it just "he's a buddha, he has no worldly desires"? Or is it "ToT is a passion project for him, all he cares about is making a great game". First one is ridiculous, and second one is suspect because we know that Bo doesn't put a lot of effort into ToT.
Even from the start Bo has reused a lot of drawings for his CGs. Scarlett and Yvonne have the exact same feet just with different coloured nails, for example. The ONLY 100% original update ToT has ever gotten was Ms. Claus' floor. Sometimes when he reuses art he changes the shape a little, changes the texture or uses different angles so it looks different. You can probably count on one hand the amount of times Bo has had to draw soles for his game (no joke), which is very weird considering he has a foot fetish and feet are an important aspect of his game.
And then there's the fact that he puts other people's art into his game. This could be for a couple of reasons: he's either SUPER LAZY, which could be corroborated by the fact that the first time that he did it he literally copy-pasted the thing (Msize CG which became Eliza's foot), or he's insecure about his drawing skills and wants to do better for his game. Either way, if you're making a passion project and you really care about the end result, the last thing you should do is steal other people's work, or else your precious passion project would be sullied, right?
Pic related is some more proof that Bo traces some of his art.
- Left pic is drawn way better, IMO the best soles in the game
- Right pic looks ugly and amateurish by comparison
- Left pic looks dull, there's no shine except for a couple of tiny sweat drops
- Right pic has a little shine that Bo likes to draw in everything for some reason
- Left pic has short toenails
- Right pic has long toenails
- Left pic knows how to draw the little toe
- Right pic draws the little toe like it was finger
Keep in mind that Left pic was in the game BEFORE Right pic, and Right pic is supposed to be the continuation of Left pic from a different angle. Since we don't know who the artist is for Left pic this isn't 100% concrete proof, but to me it's still obvious.
There's another Khulan pic (her kick) that also seems a little too good for Bo to have drawn, and that has Khulan's foot have some kind of mole in it that never appears again. But with that one the tracing isn't as obvious as in this case, and it's possible that Bo did draw that one and is just very inconsistent with his art. Idk
TLDR: If you say Bo doesn't care about making money, then what he should care about is his art/this project. IMO If he cared about his art/this project he wouldn't fill it with low-effort reused art and plagiarized art. Some proof of more plagiarism