From the surviving documentation it appears it was based on Java 1.1.3, and called j2d, which ironically it is similar to what Java to Dex ended up being on Android.

https://scispace.com/pdf/using-inferno-to-execute-java-on-sm...

I also assume it wasn't something they cared that much about, as I could not find the original source code on the Inferno open source repo.