Actually, Azul attempted to get others interested in their technology with a "Managed Runtime Initiative" (see e.g. http://lwn.net/Articles/392307/) and released a lot of code, under the GPL as I remember.

Per https://groups.google.com/forum/#!topic/mechanical-sympathy/... the Linux kernel types had no interest in incorporating it (it requires some things like bulk page table changes with only one clearing of the TBL at the end).

No offense to Azul, but that looks sort of like them just trying to get their kernel patches into the main linux kernel for ease of deployment.

Having a pluggable scheduler and memory management module might be nice for other pauseless GCs too, but not sure how that relates to any patents Azul may hold in this area, for instance: https://www.google.com/patents/US8452938?dq=ininventor:%22Gi...

The patent issues couldn't really be sidestepped as you describe because nobody in jurisdictions which have software patents could use it.

Pauseless GC for immutable objects could be achieved easily without any patent encumbrance or OS level support. Given how widespread immutable state is, I do wonder why it's never been attempted.