Where do you get the information from that it is proprietary? As far as I see it it's licensed under BSD3-Clause [0] which is a OSS license, despite being more permissive.
That made me assume that it was proprietary, but I'm very happy to be proven wrong about this. Furthermore it looks like unlike 2.0, Scratch no longer depends on the proprietary Adobe Air component, so if that is the case, it's a big improvement!
It would be less confusing if they'd replace "Linux is currently not supported" with a link to their repository on Github. I might contact them about that.
Can't wait to try it out!
Does anyone know whether Scratch 3 supports recursion like Snap! does?
Last time I looked, I didn't manage to find it anywhere...