Is that legit or what?...
Yep
Earth model was made by Uriah to replace the Moon one. I think it's just a texture replacement in fact. You can adjust the Moon size by going in world.cfg and adding
moon-scale = x.x,
In this case my parameter was
moon-scale = 64.0,
If I'm not wrong moon-scale = 1 is normal moon size, so in these screenshots, the "earth moon" is a 222 720 km diameter planet, making it almost twice as large as Jupiter. If the earth was orbiting such a massive planet at this close distance, tidal forces would crush it into pieces
Edit: first screenshot is 64, the other two are 128, so it's 4 times as large as Jupiter in these.