It would be nice if it were open source, but I don’t see anything that’s unclear about the IP.
I don't even understand how can Mojo be compared to Python without reflecting on Python Software Foundation which is arguably the main reason Python is such a wild success. We should do more PSF not less.
Community management and language feature haggling is not worth the expense at an early for-profit company with an alpha language that needs to solve internal problems.
[1] https://www.modular.com/blog/mojo-a-journey-to-68-000x-speed...
Try to do it yourself (say take a merge sort implementation and try to make it scale), it'll be roughly this much after a few hours of work.
Now imagine the compiler is doing this for you.
You can have your python parts source compatible with the new language.
Of course they are far off from that.
But not that far off if your python code is typical ML framework consumer code.