Creating a decent DSL that consumes no more than 1K RAM is a challenge (for me at least). Certainly coding the runtime/VM in C adds to the challenge (and bloat).
However, all I really need is a looping facility, conditionals and some primitive form of global variable creation (1K is not a lot of space to get fancy and do closures, recursion and other forms of state capture).
First, thing is first: I need to study the iRobot Create Open Interface and see what kind of commands I need to send and responses I need to react to.
In the meantime, I stumbled upon this ATMega128 board. Nice price, more memory (4K RAM) and perhaps more suited to my task than the Butterfly.