If I were charging money you wouldn't say this [..] Because then there would be a contract between you and him, preventing you from doing harm. [..] but sin

If I were charging money you wouldn't say this [..] Because then there would be a contract between you and him, preventing you from doing harm. [..] but since I'm not you seem to believe you're entitled to I didn't gather that from he said at all. He (implicitly) said he doesn't trust you and won't use your software unless he is able to read the code for himself or obtains a contract that protects him from wrongdoing. Those are two ways of obtaining guarantees. You nor your software provide such guarantees and as such he will not use your software. That is not a complaint, but merely an informative statement.