It's interesting to see how many people have forked the project repository for something that's just freeware and not open source. I wonder if there was a release of the source code in the past that I might have missed?
It's a modelling tool. Pretty sure there are plenty of users (e.g. artists) who don't care at all about source availability.
And, this is why I say the license is lenient: most freeware creative tools will also try to lay their hands on what you make using them. (e.g., edu versions of modelling/CAD software will also impose restrictions on the files you make using them, meanwhile this doesn't even require attribution let alone restrictions on commercial use of the output)
I'm more interested in why people are forking the project's page when there's no app soure code. Maybe I'm missing it... do you see the source to the wonderful app?