Open source licenses, using licensed source code under new licenses

[Ben Tilly]

On Wed, Apr 2, 2008 at 2:50 AM, Ryan S. Pettigrew
<bladetooth at comcast.net> wrote:
>         I have unwittingly run into a case where I'd like to release code
> under Open Source license x, but it uses code under Open Source licenses a,
> b, and c. First, are there any licenses that a, b, c, or x could be which
> can be used together, unchanged, in this way? Second, do I need a lawyer to
> determine whether the licenses can be used together, or is it something I
> can determine on my own? Third, will I need a custom license for x, or can
> it be a standard license, in spite of having to preserve the terms of a, b,
> and c? I realize that, in general, this may fall outside the purview of your
> site or discussion; however, a license that can incorporate code from more
> Open Source licenses would be very useful.

I am not a lawyer, and this statement of what I consider common sense
is not legal advice.

If the licenses are permissive (eg BSD, MIT, etc) then you're probably
not going to have a problem.  But it never hurts to check with a
lawyer to be safe.  If one of the licenses is the GPL, then consult
http://en.wikipedia.org/wiki/List_of_FSF_approved_software_licenses
and see if the FSF lawyers think they are GPL compatible.  If they are
then you can release under the GPL but under no other license.  If one
is not then you can't release at all without getting permission from
the people you got the code from to relicense.  (At least this is so
if the FSF lawyers are right.)  If none of the licenses is the GPL but
all are listed as GPL compatible then you should be able to release
under the GPL.  If you want a more generous license you'll need to
talk with lawyers.  If one is not GPL compatible and none are the GPL,
then you definitely should talk with a lawyer to determine if they are
compatible.

If you want more specific advice, or advice that is more reliable than
some random guy on the Internet talking out of his ass, by all means
talk to a lawyer.  Then if you get advice and it turns out to be bad,
you can sue your lawyer for giving bad advice. ;-)

Cheers,
Ben