Jai, odin and zig's creators are all part of the handmade network, a community of programmers. You are vastly underestimating blow's reach/influence.

Odin's creator has credited Jai as an influence. You can see him in the comments of old jai youtube videos (videos that go into a lot of depth about the language design). Odin's syntax and features are very similar to Jai, the influence is pretty clear. Odin has other influences of course but you could say it's "jai but open source".

Lastly, jai is not open source but it doesn't mean it's not available. You can message blow to get access to it. Many programmers have used it. There are third party jai libraries on github.