From Simon Peyton Jones (recent Royal Society member) we read the paper: Implementing lazy functional languages on stock hardware: the Spineless Tagless G-Machine.
Now this paper is part of how they made Haskell a lazy language when they were implementing it, and solved some problems they had at the time.
The only comparable paper seems to be: Compiling Lazy Functional Programs Based on the Spineless Tagless G-machine for the Java Virtual Machine but there doesn't appear to be an implementation available.
One tangentially related is: Compiling Haskell to Java. However in this approach they leave the implementation of the Spineless Tagless G-Machine in GHC and just read the output.
My question is: Are there any implementations of the spineless tagless G-machine other than in GHC?