What is the GPL?
The GPL (GNU Public License) is the license that Plone is distributed under, and it governs what you can and can't do with the Plone code. Very shortly summarized, it says that you have to release any changes you make to the code base back to the Plone community if you are redistributing Plone. There are a number of additional questions arising from this however - so we've tried to answer most of them in this document.
Which version of the GPL is used?
Plone uses GPL version 2 as its license. As of summer 2009, there are no active plans to upgrade to GPL version 3.
Where can I find the text of GPL?
It's available at gnu.org.
Will Plone cost money in the future for either clients or developers?
No. Should the Foundation offer a non-GPL-licensed version of Plone, then commercially licensed versions of Plone would be able to do this, but they would be products separate from the Plone you are currently using. A company may choose to license the Plone source code and sell it as a separate product, but the Plone you are using now will always be under an Open Source license.
Is Plone available under a dual-license?
At this time, Plone is not available under licenses other than GPL, nor has it ever been. As of May 2009, the Plone Foundation has adopted a policy through which it may choose to relicense a limited number of Plone's *framework component modules* under the modified BSD license in order to make it easier for developers to re-use these modules outside of Plone. This does not affect the overall licensing status of Plone. See our "Framework Components Relicensing Policy":http://plone.org/foundation/materials/foundation-resolutions/plone-framework-components-relicensing-policy for more information on this policy.
Are there any differences regarding licenses and costs when using Plone commercial and non-commercial settings?
[See note above for current state of dual-licensing.] No. Plone is issued only under the GPL. We make no distinction between for-profit and non-profit use.
Will it ever cost money to upgrade a current Plone installation?
When developers give source code back to the Plone community, will the Plone Foundation at a later point then include this code in a future commercial release of Plone?
If it's checked into the Plone SVN (not the Collective) as a change to Plone itself, both the Plone Foundation and that developer has full rights to that piece of code. So if Plone Foundation licenses Plone under a commercial license, that code will be part of the package.
Must code I contribute to Plone be GPL?
In order to become a contributor to Plone, you must sign the Plone contributor agreement, through which you assign copyright in your code to the Plone Foundation. All Plone Foundation-owned code is released under the GPL, except for selective libraries released under the BSD license as described above. So, yes, if you checkin a new package to the core Plone code repository, you must check it in with a GPL license. You, as the code author, do not get to choose which license under which to release the code.
Must add-on products for Plone be licensed under the GPL?
In most cases, yes. The GPL covers any "derivative works" of Plone and defines these derivative works as those which:
- copy or modify the code we provide to you (this includes Python code, HTML, images, etc.)
- links to our GPL'd Python code (eg, by using Python's "import" statement)
The vast majority of add-on products exhibit one or both of these behaviors, and, as such, must be licensed under the GPL. It is possible to create an add-on product that does not exhibit these behaviors (many generic Zope products that are not specific to Plone, and some Plone themes, do not). Such products need not be licensed under the GPL.
Must theme products for Plone be licensed under the GPL?
Yes, if the theme product imports from GPL-licensed code. See the "Plone Theme License Policy":http://plone.org/foundation/materials/foundation-resolutions/plone-framework-components-relicensing-policy for more information.
Why aren't you using the LGPL?
The GPL is well-understood by most companies because of Linux, and meets our community's goals better than the LGPL.
Can the Plone Foundation change the license of Plone to (for example) the BSD license?
Yes. The currently released code will always remain GPL, however. If we should ever decide to change the license, for example the BSD or Apache licenses, we would probably have parallel licenses, so you could choose what fits your needs best. Even if we decided to change to BSD from GPL, the GPL version would still be available and be developed.
I have developed a company intranet, and made some changes to the Plone core that contains business-sensitive details. Do I have to release these publicly?
No. As long as you aren't redistributing the code (e.g.: selling it as your product or distributing it outside your company), you can keep any changes that you do to Plone for yourself. We do appreciate contributions and bug fixes, though. :)
Will I lose the rights to code I contribute to Plone?
Absolutely not. You have full rights to do whatever you want with that piece of code, and the Plone Foundation have full rights to modify that code in the Plone code base.
So why can't I take Plone, change it around a bit, modify the sources and sell it as my own product?
You can. Nothing in the GPL prevents you from re-selling Plone, as long as you meet the terms: you must ship full source code, for Plone, any changes you make, and any add-on products. In addition, you must license your product under a GPL-compatible license, and you cannot use the name "Plone" for any modified product--"Plone" is a registered trademark. So, you can sell your own version of Plone: you just cannot do so as a non-GPL-compatible product, nor call it "Plone."
What is this bit about responsibility for code checked into Plone in the contributor agreement?
You are responsible for not checking in copyrighted code - this is a precaution we have to do, as we don't have the resources to check code contributions from everyone. It does not mean we will sue you because your code has bugs.
I suspect that company "X" is marketing and selling Plone as their own system and/or using Plone code in their product without contributing the changes back to the community. What should I do?
Please email the Foundation Board with details of where you found the product and why you think they are using Plone code. We will then contact the company, and see if they are infringing on the GPL, and let our lawyers have a look at it.
I have additional questions that are not answered by this FAQ.
Feedback and additions to this document should be sent to the Foundation Board and this document will be updated accordingly.