[Zope] ZPL and GPL: What should one consider when choosing a license?

[Ross Patterson]

Recently, someone wrote to me regarding one of my z3c packages which is
licensed under the GPL.  They asked me to license them under the ZPL
saying that the ZPL would allow the widest range of use for those
packages.  They also implied that using the GPL impacted the licensing
of other code that uses mine.

Mostly this is just a debate I've never taken up before.  I've always
just chosen the GPL because it's the most aligned with my values and
ideals on a "visceral" level.  IOW, it's a gut choice not an educated
choice.

I realize this is an old debate.  I found some lengthy threads on
zope-dev from 2001, but I think there have been some license changes
since then.  I also read the following blog posts:

http://radio.weblogs.com/0116506/2005/11/21.html#a370
http://awkly.org/2005/11/21/gpl-considered-harmful/

Unfortunately, the comment by Chris McDonough mentioned in the latter
doesn't seem to be accessible any more.  I'd love to read it.

>From those blog posts, I don't really see any corroboration of the
claims of the person who made the request that I switch to the ZPL.
What exactly about the GPL narrows the range of developers who can use
my code?  What about the GPL impacts the license of other code that
depends on my code?

Here's what I want.  I want anyone who modifies or forks my code to make
their modifications just as accessible to myself and the community as my
code is in the first place.  I also want anyone who forks my code to
credit me and other contributors as authors of the code they forked.  I
have a slight preference to allow proprietary code to depend on my code
without having to open source their code.  I definitely want commercial
entities to be allowed to sell products and services that include my
code as long as credit is given to the authors.

That's just what I want from my admittedly naive perspective.  I'd
like to hear comments on why others think I should or shouldn't want
any of those things from a license.  I'd also like to hear how others
think the license available relate to what I want from a license.

Thoughts?  Is there documentation somewhere about choosing a license?
Maybe a howto I missed in my googling?

Ross