Of course it can be used on iOS, there are commercial applications that do exactly that. You can turn off the JIT and you're left with probably the fastest interpreter for a dynamic language that currently exists.

LuaJIT is state-of-the-art even without the JIT. A lot of people miss this and go down various rabbit holes only to come up with something that's significantly worse. Personally, given what I just described, I don't see how Gravity compares at all favorably to Lua.