Dual licensing -- other wrinkles

[Rick Moen]

Quoting No Spam (nospam at pixelglow.com):

> 1. Can I simply write a preamble in my headers saying "if you didn't
> pay for this, it is licensed under GPL; if you did pay for this, you
> can either choose GPL or (unnamed commercial license)"?

I don't see why not.  It's reasonably common to let recipients choose to
accept the codebase under one or another of two (or more) alternative
sets of licence conditions.  OpenOffice.org does so, for example.

However, in that hypothetical, a recipient who then elected GPL terms
could then turn around and pass it on to other parties likewise under
GPL terms (without necessarily paying you or anyone else).  You might
dislike not getting that second-level revenue; however, as with all
copyleft licences, you as copyright holder would be the only one with
the legal right to include the codebase in proprietary (or other
differently-licensed) derivatives.

(I'll assume, by the way, that in saying "unnamed commercial licence",
you mean "unnamed proprietary licence".)

> 2. I'm not interested in the complexities of collecting sublicensing
> and subsublicensing fees -- all I want to do is, if you pay for it,
> you can use it any way you see fit, including except that you can't
> sublicense it as anything else but GPL. 

Sounds like.  I've been pointing out, for years, this way of using
copyleft to protect one's monopoly on certain ownership rights (such as
proprietary derivatives).  It's interesting to hear someone else mention
the possibility.

> Would the header preamble handle this? Is it sufficient for the other
> license to be some sort of permissive non-reciprocal license like CPL,
> BSD, etc., or do I have to put more teeth into it?

Standard answer:  The right licence depends on what you want to achieve
with your property.  (But I think I'll be addressing your concern more
precisely, below.)

> 3. Suppose at some later stage, I discover another GPL'ed derivative
> of my work in the wild. Does the fact that I have dual license mean
> that if the other author says, "I don't want to submit this code back
> to you under your dual license", I cannot then incorporate his code
> back into my dual licensed code base?

Consider:  The other author can apply to his personally-written code
whatever terms of use he wishes.  If his chosen terms don't clash with
yours, then he can redistribute the derivative work created by combining
his work and your earlier one, without violating your copyright.  (In
your hypothetical, a qualifying licence choice on his part would be any
licence that does "not impose any further restrictions on the
recipients' exercise of the rights granted" by the GPL as to your
portion of the dervative work (GPLv2 clause 6).  That could be a
permissive (BSDish) licence, it could be pure GPLv2 terms, it could
be the same terms you specified (dual-licensed), or any number of
others.

What you're really like, of course, would be to get the other author's
work under the same terms you specified -- dual licensed.  Presumably,
you'd have to work out with him the revenue arrangement to divide fees
from users electing [unnamed proprietary licence].  Coaxing the other
author into granting that specific permission bundle might require
paying him; you could alternatively just buy his copyright title.

-- 
Cheers,             "Don't use Outlook.  Outlook is really just a security
Rick Moen            hole with a small e-mail client attached to it."
rick at linuxmafia.com                        -- Brian Trosko in r.a.sf.w.r-j
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