Dual licensing

[Nick Moffitt]

nospam+pixelglow.com at pixelglow.com  quotation:
> I'm seriously thinking of dual-licensing my software library macstl,
> in the style of Qt, mySQL, Berkeley DB et. al. with a GPL and a
> commerical license I have some questions though.
> 
> 1. Doesn't the GPL prohibit un-GPL'ing the code? Or does dual
> licensing rely on having files with identical content but different
> licenses?

	Think of it this way:  Copyright starts with "all rights
reserved", except that implicit rights may be inferred from your
actions (for example, if you hand a copy of a work to someone, it's
difficult to make the case that you didn't want that person to use or
read it).

	So you have to grant permission to people to do various things
with your work.  It can be as simple as telling them "Sure, go ahead.
Share it with whomever you like."  In order to be as clear as possible
in the eyes of the law, however, we often write these permissions in
deliberate legalese.  No matter how it's written, we call the grant of
permission a license.

	You can write them in legalese, plain English, German,
Esperanto, or Klingon if you want.  The important question is "Who's
opinion on the exact meaning of this license will be most important in
the event of an argument?"  For most cases, it will be the courts of
whatever country the argument is in.  That's why we tend most often
toward the legalese.

	The FSF has a soft spot for plain english licenses, but
understand the need for a clear legalese license.  That's why you have
the preamble in the GPL, and why Bradley Kuhn loves to chuckle over
the official certification of the phrase "DO WHAT THE <redacted> YOU
WANT" as an FSF-approved Free Software License.

	Now, you, as the author, release to the world your work under
the terms of the GPL.  You're basically saying "you folks can modify,
redistribute, etc., BUT you have to meet these few conditions
(copyleft, mostly)."  You're also perfectly free to say "OR, you can
get permission to do these various things with my work, provided you
meet these OTHER conditions (pay a license fee, agree not to share the
work, etc.)".

	That, in a nutshell, is all that dual-licensing is.  You
basically hold up your work and say "You can get a copy under THESE
conditions, or under THOSE conditions.  Pick the one you like."  If
both licenses are of a public nature, you can also allow people to
propagate the dual license nature.  This is, for example, how some
projects dual-licensed under the GPL and the TrollTech license, or the
GPL and the MPL.

	Just remember that all a license amounts to is a statement
that you are giving a copy of a work to someone with certain rights
and responsibilities attached.

> 2. I'm uncomfortable with making contributors assign copyright to
> me, just so I can dual-license. Would it be sufficient to get them
> to send me a form email stating that they agree their contribution
> will be dual-licensed?

	That should be acceptable, but you might find yourself having
to track these people down later if you wish to revise your non-GPL
license.

	Basically you're having the contributors license THEIR work to
you with the permission to dual-license.  You may wish to provide them
with the license under which they give you their work, with a clause
that allows you permission to update the licenses you release the
derived work under (use the "or, at your option, any later version"
bit of the GPL statement, and cook up something similar for your
non-GPL license).

> 4. The GPL obviously doesn't prohibit commercial activity on top of
> the software, since Red Hat et. al. use services as a commercial
> model. Is there any OSI-certified license that would either
> encourage or compel commercial activity to have to use a different,
> commercial license? E.g. I note that the mySQL site phrases this as
> "quid pro quo" but not an enforceable requirement.

	Typically dual-licensing with a proprietary license is seen as
a buy-out.  Recipients may buy out their responsibilities under the
GPL, which they may be uncomfortable with.  Since the OSD requires
that the license may not restrict fields of endeavor, I believe that
discomfort with copyleft is going to be your most compelling argument
for your non-GPL license.

-- 
"virii" would be the plural of the mythical masculine          Nick Moffitt
noun "virius". The neuter plural of "virus" would be     nick at teh.entar.net
"vira" (as "opus" & "opera"), and "viri" is the plural
of the masculine "vir" (man). It really is "viruses"!
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