Alan Wolfe wrote:

> I want to use libcurl in a commercial product and was wondering if I
> had to do anything special to be able to do so?

You really need to hire a lawyer and ask him or her that if you want to
be sure. No one here or on any mailing list is going to be able to give
you a definitive statement of any kind.

That aside, you can read the license yourself, it's pretty simple:
<http://curl.haxx.se/docs/copyright.html>. This is the standard MIT/X
license <http://en.wikipedia.org/wiki/MIT_License> modified with the "no
using the copyright holder's name in promotion" line. There's really
not much that you aren't allowed to do with such a license.

> I know about including the license.txt requirement but i was wondering
> is there anything else?

Don't be confused with the old "BSD 4 clause" license which required you
to acknowledge the software in advertising materials. There's no such
requirement with the MIT/X license.

> Also our product is using zlib but since zlib is already a part of
> libcurl does anyone know if we have to do anything special for that?

zlib is not "a part of curl". curl links with zlib just like a million
other software packages out there. That doesn't mean the zlib license
is in any way modified by the fact that curl happens to be one consumer.

> Or would satisfying libcurls needs be enough to satisfy zlib as well
> since zlib is contained in libcurl?

Again, it's not. A package does not subsume another just because they
link with each other. The license that is associated with a given piece
of code does not change based on where you found it.

You must simultaneously satisfy the individual conditions of each
license for every piece of code that is linked into the final binary.
And anyway, the zlib license is just as permissive as curl's:
<http://en.wikipedia.org/wiki/Zlib_license>. Seriously, when it comes
to licenses it couldn't get any easier than MIT/X and zlib which pose
almost no requirements, at least compared to e.g. GPL.

The real problem however is not the license of curl (which is as
permissive as possible), it's the fact that curl typically links with a
lot of libraries and again you have to simultaneously satisfy them all.
See <http://curl.haxx.se/legal/licmix.html> for some details.

There is one noteworthy trap that distros have to be wary of: the
openssl license is incompatible with GPL. This means if you build a SSL
enabled libcurl (using openssl) then that libcurl cannot be used by
other GPL apps (unless those apps have specifically exempted openssl.)
This is particularly annoying for distros because they might not know
all the possible things that libcurl might be used with, so they
wouldn't necessarily know if somehow the combination of
openssl+libcurl+anything_GPL accidently was linked. Anyway, that's
probably not a concern for you and if it is, you can always use an
alternative SSL lib.

> I know this may not be the right place to ask about zlib requirement
> but just hoping someone can help me figure out this legal labyrinth :P

A lawyer under your hire is the only person who can truly help you.

Brian
Received on 2008-03-11