Hallo Hikarus

On 15.05.2018 16:20, Hikerus wrote:

But the copyright of postal codes is by Swiss Post.

Postal codes per se are probably not copyrightable or otherwise legally protectable. A list/database of postal codes might be protectable, though.

So I did it wrong

Not necessarily. What was your source for this change? Your local knowledge (because you're one of the people receiving letters there)? Then everything is fine. (Except that the postal code might not be valid for the whole village, but that is a correctness issue, not a legal one.)

If however your source was a copyrighted or otherwise protected database or list, be it by Swiss Post or anyone else, then the situation would different.

How can you determine what your source was? Well, did you have to actually look up your postal code somewhere, or did you already know it due to regular usage?

I have to change back to the wrong one?

No, that'd be pointless, as potentially illegally copied information would remain in OSM's history. The data working group (DWG) of the OpenStreetMap Foundation can redact such legally problematic changes if necessary, which will remove the information in question also from the history.

Regards,
Raphael