There have been vastly superior systems to Unix but with commercial licenses.
https://en.wikipedia.org/wiki/Inferno_(operating_system)
TL;DR: The Unix people make a Java.
I was a teen at the time, but in hindsight, in '96-97 'open source' from commercial vendors wasn't the norm, and Lucent finding income from openInferno would've been big change in business model.
Java was meant to be familiar to C/C++ programmers, of which there were a lot. I'm not sure how Limbo would compare in terms of learning / productivity. And would there have been a Windows native "Inferno/Limbo" IDE type thing. (If there was one, please let me know)
Inferno would've needed a killer app. I assume it'd perform better than Java, and at the time it would've competed with small Java applets. Java desktop didn't happen, I recall Corel trying and failing to port Word Perfect to Java. I don't know how if anybody ever tried to write an office suite in Limbo.