A central software development system comprises a code processor and a code authenticator. The code processor converts modified free source code received by the system to program code such as executable code or bytecode. The code authenticator selectively signs the program code using an encryption key associated with one or more devices for which the program code is designed, e.g., a computer or mobile phone. The central system may also include a code scanner. The code scanner verifies the modified free source code, e.g., by scanning the modified free source code or intermediate code generated by the code processor for impermissible code patterns. The code authenticator signs the program code if the modified free source code is verified. The impermissible code patterns may correspond to at least one of proprietary, malicious or virulent code sequences.