I wrote on sf.net:
"XOOPS currently uses the GNU-General Public License. This means that (as many of you know as you've taught me this yourself) when a module shares the core processes to a degree of dependancy, the module automatically fall under the same license."

The FAQ states:
"If I create a module for XOOPS, do I have to release it as GPL?

The GPL has exceptions that allow you to use GPL software and write your own extensions without releasing your code as GPL (I won't go into what's a module or not which is covered under GPL).

wfsection wrote:
There is nothing stopping you the developer charging for your software and restricting the usage under GPL.

wfsection wrote:
You could state that the code maybe modified for personal use but not redistributed in any form.

Why does the GPL permit users to publish their modified versions?
A crucial aspect of free software is that users are free to cooperate. It is absolutely essential to permit users who wish to help each other to share their bug fixes and improvements with other users.

Some have proposed alternatives to the GPL that require modified versions to go through the original author. As long as the original author keeps up with the need for maintenance, this may work well in practice, but if the author stops (more or less) to do something else or does not attend to all the users' needs, this scheme falls down. Aside from the practical problems, this scheme does not allow users to help each other.

Sometimes control over modified versions is proposed as a means of preventing confusion between various versions made by users. In our experience, this confusion is not a major problem. Many versions of Emacs have been made outside the GNU Project, but users can tell them apart. The GPL requires the maker of a version to place his or her name on it, to distinguish it from other versions and to protect the reputations of other maintainers.

wfsection wrote:
The whole point of a license is to protect your work and give you the developer rights over it.

The GPL protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

In effect, the GPL is a copyright patent that guarantees that the souce code of a software package remains public property over time. The results of this license create a scenario where you have the legal freedom to copy, distribute and/or modify the 'said' software in accordance with your personal or business computing needs. What you cannot do is remove the General Public License from the software, in effect giving everyone else the same freedom to copy, distribute and/or modify the software source code. Free software is not necessarily without cost, and you are also free to charge for distribution of GPL software and / or the inclusion of a warranty or support service with, or without, modifying the software source code yourself. Hence, you cannot sell GPL software, but you can charge a fee for support, warranty, distribution, consultation, dvd-burning, etc.

So, what is the GPL? The GPL is a software patent that, in effect, guarantees public freedom to copy, distribute and/or modify the software with, or without charging a fee subsequent to the clause that removal of the GPL from the said software entails a violation of the patent agreement inherent to the GPL license itself.

wfsections wrote:
There is nothing in the GPL to state than you can/cannot put restrictions on your work at all.

Does the GPL allow me to require that anyone who receives the software must pay me a fee and/or notify me?
No. In fact, a requirement like that would make the program non-free. If people have to pay when they get a copy of a program, or if they have to notify anyone in particular, then the program is not free. See the definition of free software.
The GPL is a free software license, and therefore it permits people to use and even redistribute the software without being required to pay anyone a fee for doing so.

If I distribute GPL'd software for a fee, am I required to also make it available to the public without a charge?
No. However, if someone pays your fee and gets a copy, the GPL gives them the freedom to release it to the public, with or without a fee. For example, someone could pay your fee, and then put her copy on a web site for the general public.

I just found out that a company has a copy of a GPL'ed program, and it costs money to get it. Aren't they violating the GPL by not making it available on the Internet?
No. The GPL does not require anyone to use the Internet for distribution. It also does not require anyone in particular to redistribute the program. And (outside of one special case), even if someone does decide to redistribute the program sometimes, the GPL doesn't say he has to distribute a copy to you in particular, or any other person in particular.
What the GPL requires is that he must have the freedom to distribute a copy to you if he wishes to. Once the copyright holder does distribute a copy program to someone, that someone can then redistribute the program to you, or to anyone else, as he sees fit.

Can I release a program with a license which says that you can distribute modified versions of it under the GPL but you can't distribute the original itself under the GPL?
No. Such a license would be self-contradictory. Let's look at its implications for me as a user.
Suppose I start with the original version (call it version A), add some code (let's imagine it is 1000 lines), and release that modified version (call it B) under the GPL. The GPL says anyone can change version B again and release the result under the GPL. So I (or someone else) can delete those 1000 lines, producing version C which has the same code as version A but is under the GPL.
If you try to block that path, by saying explicitly in the license that I'm not allowed to reproduce something identical to version A under the GPL by deleting those lines from version B, in effect the license now says that I can't fully use version B in all the ways that the GPL permits. In other words, the license does not in fact allow a user to release a modified version such as B under the GPL.

wfsections wrote:
I know many companies that release their software under GPL, charge for and impose restrictions on its usage and redistribution.