alt Hacker NewsHow have you found a SCO note, which never did nothing relevant for Java?
Here from Oracle, as historically taken from Sun documentation for JDK 1.1.
=> Many-to-Many Model (Java on Solaris--Native Threads)
https://docs.oracle.com/cd/E19455-01/806-3461/6jck06gqk/inde...
I think there's a naming confusion here. You said "M:N threads, aka green threads". However, your linked document clarifies that "green threads" are the M:1 threads that "[do] not exploit multiprocessors" (see the "Green Threads" parenthetical in the first subheading). It is interesting that JDK 1.1 also had an M:N threading model, but that's not what people usually mean by green threads.