[Coin-discuss] Open-source Modeling Languages

[Michal Kaut]

>> A third issue is licensing.  Since building an application that uses
>> OS practically requires linking with OS libraries, you have to make
>> sure that the CPL used by OS is compatible with the library that you
>> use for your software.  Unfortunately, I don't think that this is true
>> for the GPL.  For example, suppose that the authors of GLPK wanted to
>> produce a version of their software that took as input a model in
>> GLPK's modeling language, produced an OSiL instance, invoked a solver,
>> and then got back the result in OSrL.  Could a binary version of this
>> code be distributed under the GPL?  I believe that the answer is no.
>>
> It seems like this would violate the GPL rather than the CPL.  We 
> selected the CPL license because we felt in was more flexible.

I am not a lawyer either, so please correct me if I am wrong:

Since CPL is very generous about the usage of the code, the authors of 
GLPK could indeed include any CPL-licensed code into GLPK and distribute 
the whole package further under GPL - both as a source and as a binary 
(+ access to source, as GPL requires).

On the other hand, if any COIN-OR project wanted to use some GPL'ed code 
(such as a part of GLPK), the whole package would have to switch to GPL. 
  (This is one of the main features of GPL license, based on the idea 
that this way the open source (read GPL) will spread and eventually 
conquer the world - while people from the "other site" call it a "viral" 
license.)
This is why some of the previous emails mentioned that we would have to 
ask very nicely the authors of GLPK to allow dual licensing, i.e. to 
release GLPK under both GPL and CPL - though I am pretty sure they won't 
do it, for the above reason.

On the other hand, it is important to remember that all these licences 
are about re-distribution of the code. You as a user can freely mix 
COIN-OR and GLPK code, as long as you do not distribute the code 
further. This is why some of the COIN-OR codes have the "Third Party" 
bit, including only scripts to download libraries that are under 
licenses that are not CPL-compatible. This way, the user can download 
the libraries (and COIN is safe, since they do not distribute them) and 
then it is up to the user to adhere to all the licenses involved.


Hope this helped.

Regards,
Michal