The VM, the AST parser, and the Bison/Flex frontend are built in a layered manner: you could (with the appropriate Makefile) build only the VM, the VM+the AST parser, or all three. I don't currently have Makefile options for this, but it would be pretty trivial to add.
How long did it take to write this once you had all the ideas? I looked at the github history but they only went back 5 months and it looks like there was already a significant amount written so I couldn't tell how far back from there it went.
