For anyone who considers this interesting and/or looking for alternatives: apart from the well-known Lua there's also MicroPython [1] whos specs actually read a lot like the specs of Gravity but then some more (well, it's Python 3.5 minus a couple of features, also compiles with C99 compilers, is fairly small for being a Python, embeddable, more mature at this point, been tested on more platforms/architectures, ...).
[1] http://micropython.org/ https://github.com/micropython/micropython/