The copyright situation regarding zmac is not totally clear.
This is what Russell Marks had to say when I asked him:

"
> [...] I would
> like to make double sure that zmac is indeed public domain and so
> freely distributable and modifyable.  Can you confirm this?  Have the
> various authors of zmac over the years agreed to give away their
> copyright?

This is a difficult area, partly because I'm not a lawyer. :-) None of
them seemed to explicitly give away their copyright, but equally, none
of them asserted it either. If you really want to be sure that it's
all entirely public domain, the sort of thing that would definitely
stand up in court, you'll have to try and contact all three previous
contributors (my changes are definitely PD, you wouldn't have to worry
about that). I have vague memories of seeing both Colin Kelley and
John Providenza's names mentioned in more recent things than zmac, but
I don't know any contact addresses for them (nor for Bruce Norskog).

OTOH, if you're just after some general reassurance that it's ok to
distribute a hacked version, I'd say it's fine - if nothing else,
Colin Kelley posted it to comp.sources.unix in 1987, so he must have
thought it freely distributable and modifiable (the latter because he
made changes himself). I think an earlier version had featured in
simtel's "UNIX-C" directory too.

Also, this point from the copyright FAQ may be relevant:

> 2.2) What is "public domain?"
>
> In contrast to copyright is "public domain."  A work in the public domain
> is one that can be freely used by anyone for any purpose.
>
> It used to be that if a work was published without notice, it lost all
> copyright, and entered the public domain.  That's no longer true, and now
> public domain is more the exception than the rule.
>
> There are still a number of ways that a work may be public domain.
[...]
>  - The copyright might have been forfeited.  For example, the work
>    may have been published without notice prior to the change in
>    the law that eliminated the notice requirement (March 1, 1988,
>    the effective date of the Berne Convention Implementation Act,
>    PL 100-568, 102 Stat. 2853).

zmac was published without a copyright notice in 1987 (and, one
assumes, long before then as well). This is the main reason I describe
zmac as public domain - the 1987 posting was published source with no
copyright notice and no license being distributed for free by one of
the authors. That smells of PD to me, even without the above. :-) I
just don't see what else it could really be. But getting real,
legally-sound confirmation of this would be a challenge.

I know this isn't the "yep, no problem, and here are all the authors'
current addresses so you can check for yourself" you may have been
looking for, but there it is.

FWIW, I distribute zmac with ZCN (my GPL'd CP/M-like OS for the
Amstrad NC100). In case that contributes anything to this. :-)
"

[Needless to say, I too forfeit any copyright claim on my changes!]

I am therefore assuming that zmac is public domain (note, however,
that the Act above is probably an American one and different
conditions may apply in e.g. the European Union).  I am not a
lawyer, though, and I would strongly suggest you don't abuse this.
In particular, I wouldn't use zmac or portions thereof in any
commercial product.

If any of the authors of zmac requests so, I will immediately
withdraw this release.


Mark RISON, <mrison@hotmail.com>, 1999-07-19
