[xmlvm-users] Clarifications on the Linking Exception

[Arno P. <ar...@pu...>]

Guys,

there have been some questions regarding our licensing model. I would 
like to take this opportunity to express our (i.e., the XMLVM Core Team) 
intent. Before I go into details, I want to point out that our goal is 
to create a fair model that serves both the XMLVM Core Team as well as 
contributors. We acknowledge that some of you are interested in using 
XMLVM for commercial purposes. We ask you to acknowledge that we have 
legitimate business interests as well. The goal is to find a balance 
that works for all of us. XMLVM is and always will be Open Source. We 
use the GPL license and as many of you know, this license is very 
restrictive. The GPL license requires you to put your own source code 
under the GPL license. If you are just doing Open Source work, this is 
usually fine, however, if you want to develop commercial applications, 
this is not acceptable for obvious reasons. That is where the idea of 
dual licensing kicks in. We offer a second, commercial license, that 
will allow you to develop proprietary products based on XMLVM. Note that 
the idea of dual licensing is not new. Projects such as MySQL and JBoss 
have been doing this for a long time.

Our commercial license is a non-transferrable GPL Linking Exception (or 
just linking exception for short) that takes away the 'viral' component 
of the GPL. This means, if we grant you a linking exception, you are 
*not* required to release your own application that is based on XMLVM to 
the Open Source. This linking exception is not transferrable. You cannot 
transfer this right to your customers.

What is somewhat new with XMLVM is that we still want XMLVM to be a 
community project. That means, we hope and encourage the community to 
make contributions to XMLVM. It is important to us that we do not leave 
the perception of exploiting contributors via our commercial license. 
For that reason we have come up with a way to 'reward' outside 
contributors: If you make a (non-trivial) contribution to XMLVM, we will 
give you a commercial license (i.e., non-transferrable linking 
exception) that will allow you to develop a commercial application with 
XMLVM without sharing your proceeds with us.

Of course there are some details that need to be clarified and there 
have been some questions on the mailing list regarding the details. Let 
us make a specific example: you send us a patch to XMLVM that is 
non-trivial (lets not get into the discussion on what is a non-trivial 
contribution. There is obviously no objective way of measuring the 
quality of a contribution. We will make that call on a case-by-case 
basis). If we (the XMLVM Core Team) agrees to merge your patch with the 
code base of XMLVM, we will give you a non-transferrable linking 
exception in return. In terms of the scope of this non-transferrable 
linking exception, there are several components: (1) to which version of 
XMLVM does the linking exception apply? (2) who is the recipient of the 
linking exception? (3) what is the duration of the linking exception? 
Let me address these issues individually.

(1) we do not maintain an official versioning scheme for XMLVM. Things 
happen so fast in our code base that we do not plan to introduce 
official version numbers. In the future we might change this, but for 
now, we simply refer to the Subversion revision numbers. The linking 
exception is issued for the version of XMLVM that includes the 
contributors patch and any version of XMLVM released in the following 6 
months. For really significant contributions we are willing to extend 
that time frame.

(2) the linking exception is issued to the contributor of the patch. 
This can be an individual or the company for which the contributor 
works. This will allow the individual/company to develop applications 
that can be sold to their customers without having to share revenues 
with the XMLVM Core Team. The linking exception *cannot* be transferred 
to the customers of the contributor.

(3) for the versions of XMLVM for which we issue the linking exception, 
the usage is not limited to the aforementioned 6 months. I.e., 6 months 
after you made your contribution you may still use older versions of 
XMLVM for commercial purposes. Only if you want to benefit from new 
features introduced to XMLVM after those 6 months, you will need to make 
another contribution to XMLVM to extend the duration of the linking 
exception.

I would like to start a discussion with you guys on the mailing list to 
refine these rules. Again, we want to strike a balance between your 
legitimate commercial interest and ours.

Let me know what you think.

Arno