[asterisk-users] Licensing question.

[Kevin P. Fleming]

On 11/08/2011 04:47 PM, Yaroslav Panych wrote:
> Greetings
>
> I have found next paragraph in Licence file(source root)
> "Digium, Inc. (formerly Linux Support Services) holds copyright
> and/or sufficient licenses to all components of the Asterisk
> package, and therefore can grant, at its sole discretion, the ability
> for companies, individuals, or organizations to create proprietary or
> Open Source (even if not GPL) modules which may be dynamically linked at
> runtime with the portions of Asterisk which fall under our
> copyright/license umbrella, or are distributed under more flexible
> licenses than GPL."
>
> What does it mean? Does it mean I can write non-GPL modules(BSD, MIT,
> etc)? Can I build my modules in common asterisk source tree(i.e. using
> LOCAL_MOD_SUBDIRS="my_mod_subdirs_list" make ) or must use separate
> tree? If so, then since Asterisk core does not accepts anything except
> AST_MODULE_INFO(ASTERISK_GPL_KEY, ....) what I should do here?

Asking for people on this list to tell you what 'this means' is like 
asking people on this list to tell you what is wrong with you if you 
have a headache and a fever; you will get answers, but they won't be as 
useful as if you asked an expert in that field of inquiry :-)

In spite of that, I'll give you Digium's interpretation of what that 
paragraph means and attempt to answer your questions. Since Digium is 
the 'licensor' in this equation, our opinion certainly carries some 
weight, but you should consult with your own legal counsel in order to 
determine whether the actions you wish to take are compatible with the 
license terms or not.

The paragraph you quoted above doesn't directly grant you any rights at 
all; it is only a statement that Digium can, and does, grant third 
parties the ability to produce and distribute works that could be 
classified as 'derivative works' of Asterisk without being subject to 
the provisions of the GPL version 2 (as they would otherwise be, since 
most people receive Asterisk under that license). If you have a need for 
such a license, you should contact Digium to inquire about it.

As far as your other questions go, they are fairly vague, but I can 
attempt to answer them:

* The GPLv2 places no restrictions on what you can 'write', it only 
places restrictions on your distribution of things that you write that 
could be considered 'derivative works' of a GPLv2-covered work (in this 
case, Asterisk). If you write something that could be considered a 
derivative work, and you wish to distribute it, then the GPLv2 obligates 
you to distribute that work under the GPLv2 or a compatible license. 
Most versions of BSD-style licenses, the MIT license, and many others 
are GPLv2 compatible. Many open source licenses are not; the Free 
Software Foundation maintains a page on their website covering this topic.

* The GPLv2 places no restrictions on how you build your works, where 
you place the source code, or anything of the sort.

* The module loader in Asterisk, as distributed by Digium under the 
terms of the GPLv2, does make a simple check to ensure that modules that 
are being loaded into a running Asterisk instance claim to be licensed 
under the GPLv2 (or a compatible license) themselves. This is an effort 
to ensure that someone distributing such a module will be aware that 
they need to consider the license under which they distribute it. If you 
want to produce your own modules and distribute them inside your 
organization without putting the ASTERISK_GPL_KEY into them (although 
for distribution inside your organization this won't really make much 
difference), you can certainly modify the module loader to skip this 
check (you do have the source code, after all).

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
Jabber: kfleming at digium.com | SIP: kpfleming at digium.com | Skype: kpfleming
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at www.digium.com & www.asterisk.org