https://itresearch.en.ecplaza.net/
If I bought the system, I bought the code.
Functional expressions are not copyrightable. If I own a copy of the code you wrote, I am reasonably allowed to extract those purely functional expressions into my own work. Purely creative expressions are still protected by copyright. (This is why you cannot copyright an encryption key.)
When no “owner” exists, the licensing agreement is no longer valid. Copyright is a different issue. See above.
If the code is covered by patents, extracting it doesn't give you anything that reading the public patent wouldn't (if the patent was written as it should have been, to inform, and not obfuscated or ran through incomprehensible legal jargon).
And if it's a trade secret, then you relinquished it the moment you sold objects containing it. Though I realize DRM/anti-reverse engineering laws are trying to take away our right to examine how stuff works, they are absurdly immoral laws, and breaking them should never be described as "theft".