Reading the description (I didn't look carefully through the code spec) it kind of reminds me of the old Corewars. Corewars included both self-modifying code, and the possibility (actually near certainty) that your code would be modified by your hostile opponent. Short of trying to execute a DATA statement (the goal was to make the other guy execute DATA statements with all his processes) pretty much everything would execute. It was a simple language-- 10-ish "assembly" instructions and 3 or 4 addressing modes (I'm too lazy to even look through the current site to check). It was fun to have a crude display and watch processes go zipping through the core in unexpected ways.