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.
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.