Public domain software is not open-source?

[Matthew Flaschen]

Philippe Verdy wrote:
> I do think this is a rule.

You may think so, but you have yet to point to any legal basis.

> It is written explicitly in commercial licences that embed this statement of
> ownership in their text (the licence text is made specific to the product,
> at least in the initial paragraphs, but quite often too within the section
> explicitating the licence coverage).
> 
> The separate explicit statement is required in free software (I mean GPL or
> GPL-compatible).

No, it is not required.  It may be convenient for the recipient, but it 
is not a requirement.

> I can't trust any software that does not explose the ownership of rights
> explicitly, it's too dangerous because I won't know who to prosecute in case
> of problems and I will become personnaly liable for things I did not
> intended to abuse myself. It's not the licence that will protect me.

That's your prerogative.  However, that's quite different from inventing 
a requirement for the copyright holder.

Matt Flaschen