I'd also like to put in a request for either open-sourcing or a more detailed overview of the implementations, they sound really interesting.

I'll consider writing a more detailed article on the subject. Open-sourcing the code will not be possible in the short-term.

In lieu of the implementation, I'd like to know if these allocators are themselves based on malloc or if you have some tricky assembly/kernel code going on somewhere.

These allocators are based on mmap to build the arenas.

+1, for request of implementation details. I'm really curious about this.