Sure, and those extensions can run on the MIT Lisp Machine.
But we are taking about the base system. Not extensions. And why one can take those systems and for the most part just run them in another system is cause they are so similar!
The reason is as I said before, Genera is layers on top of an existing system that hasn't changed (much).
E.g, DW is of flavours on top of TV (with lots and lots of extra additions .. additions are easy to handle -- after all the DW code is like 1M of Lisp from 1989 or whatever).
The Dynamic Listener was more complicated to rip out, but mostly work. The hard part, at which I gave up, was adding all the presentations for objects and other such.