Their homepage (https://mojolang.org/) states
> The Mojo standard library is fully open-source on GitHub and we welcome contributions! We also plan to open-source the Mojo compiler in 2026.
Their roadmap (https://mojolang.org/docs/roadmap/) doesn't say anything about it.
Another language I'm excited about is Carbon. I can't wait for an MVP to actually try it. We have so many new languages incubating in the last few years!