Comment by eslaught

You can interleave Terra and Lua execution. Terra functions are JITted if you call them from Lua. You can call Lua from Terra too, though the language makes you jump through some hoops to encourage code to avoid Lua dependencies in Terra code. So "execution" is more like you'd expect from standard Lua (or Python or whatever), it's just that functions can be compiled if you want.

Of course Terra functions can also be saved out to a file too, and if you do that they're free of any dependency on Lua (i.e., no need to like liblua*.so).