Did Jon state that he intends to release as open source? I am not sure he is the guy to the stressful route. If it all he would probably go long release cycles without considering public feedback too much.

He also stated recently that he doesn't care too much about language design at a syntax level, or better said it's not his top focus as the overarching concepts are more important to him.

I think there is a chance that people may have a hard time to adopt to the language. His strong focus on gamedev will further cut down the audience. It will certainly draw a lot of attention but a massive adoption is highly questionable.

He said that for some period, the compiler will not be open source, the language will. Whether the compiler will become OS or not, I am not sure. But I think he just wants to get the spec done beforehand. I think he mentioned that the compiler code might be purchased via paid licence? I am not certain but as I am not a AAA studio, I do not care either way.