CPL
From APIDesign
Common Public License is an open source software license originally used by Eclipse later superceeded by EPL.
Most of the software projects already migrated from CPL to EPL, but one important project has not done that yet (as of January 2011): JUnit. This essay describes my experience when trying to convince my company lawyers to like CPL, so NetBeans can redistribute JUnit without problems.
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CPL is Unacceptable
We have new lawyers. The old Sun lawyers are gone and as we are getting more and more integrated into Oracle, we need to align with its culture. One of such cultural checks is to re-approve all the open source licenses used by NetBeans.
Our new lawyers seem to be concerned about CPL, the JUnit license. True, JUnit's use of Common Public License is unique and sort of archaic. I don't know about any other (important) project using this license anymore. But the CPL was found OK by Sun lawyers and we've been shipping JUnit for ten years! What can be so horrible with it that now it is a problem?
Why we are are holding the NetBeans release and getting ready to remove JUnit from our standard installation? Is not that silly? JUnit is necessary part of any serious Java development. What can we do to allow JUnit and NetBeans to cooperate?
CPL is Not Modern
OK, let's try to ask on a JUnit mailing list. Maybe the group would not mind upgrading to more modern license. At the end EPL is almost identical to CPL. So let's ask:
Don't you want to relicense JUnit to some more commonly used license? EPL would be fine. At least I have not heard any complain about EPL from our new lawyers yet. Dual licensing to CPL & EPL probably too.
Asking on a mailing list of Open source project can result into two options. Either complete silence. Or enormous amount of opinions. The JUnit community is however different. I've received quick answers with a bunch of damn good reactions and points (including reactions from people I'd never expect to be on such mailing list).
From that I have understood that Kent does not want to relicense, but rather offers commercial alternative license for companies scared of CPL.
CPL is Great!
While reading the reactions provoked by my query on the mailing list I've noticed an explanation of why CPL is so great. It is approved open source license (good), but it scares some companies (a bit similar story to GPL) so these companies rather pay (good) than redistribute JUnit under CPL. This is perfect! Open source projects need donations (read WhyGPL for details) and it seems that CPL can generate some revenue. Good!
The wording of the CPL states, that as soon as a company redistributes your software, it cannot sue you for violating its software patents. Excellent! Open source developers hate software patents in general and this is a perfect way to fight with them. Release your software under CPL, wait until Oracle (or others) use your software and then just violate any of their patents without a risk. Or wait until IBM decides to buy your rights to your software to enjoy this patent free violation too.
The things CPL can achieve are so great!
Pay for CPL
CPL seems great for library providers. However Oracle just can't effort to use it. Thus we were about to buy an alternative license, but we have a problem. While backed by a company NetBeans is open source project too!
That is why I can imagine buying a commercial license is good for closed source projects. But how can a commercial license be suitable for an open source project like NetBeans? If we want to stay open source, we cannot have a commercial license on one of our libraries! We need to have an open source one. We need to let 3rd parties to take parts of our IDE and use them in an open source manner.
I hoped the JUnit guys to have some experiences with such dual licensing, but I guess nobody knows what to in such case. Time to seek different alternatives!
CPL is Dead!
As few guys pointed on the JUnit mailing list (including the current Steward of EPL), the EPL license supersedes CPL. This means that EPL is not just more modern license, it is more modern version of the same license.
Also it turned out that the language of CPL/EPL allows anyone to upgrade the license of the covered software to the latest version of the license. In this case one can freely replace CPL with EPL without asking for a permission anyone (not even the copyright holder). Quite surprising revelation.
This means that CPL is dead and EPL can be used instead for all projects.
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