Those limitations are true of most virtual machines. Lua bytecode has no opcodes for doing I/O, invoking syscalls, or anything else that interacts outside the VM environment. AFAICT, Python is similar with the exception of some opcodes for printing to stdout. To interact with the outside environment you must load and invoke code from modules, so access is intrinsically limited by whatever modules are permitted to be loaded. In Lua a new VM state context has no modules loaded at all--not even for the string module; nor any ability to load modules--the C application needs to explicitly load the package module to register "require" in the environment.
