Before software was protected by copyright, which happened sometime in the 80's or so, in Germany software was protected by "unfair competition law". Quite simply, if A hires developers for a million to write software and sells it, and B just copies the software, that is unfair competition. However, "unfair competition" only applies if A is actually selling the software; if A doesn't sell it, then B isn't competing with A at all, whether fair or unfair. Obviously now software is under copyright, so things have changed.
With very old works the same could be done: Let them run out of copyright. However, it would be "unfair competition" and thus illegal to compete with the copyright holder. So as long as Disney is selling Steamboat Willy, it would be protected. If they stop selling it, you can copy it and even sell it freely.