Aug 19 2011

What is GPL software?

Categories: VBA Tools Dave Rathbun @ 8:53 am

Wordpress (the software that powers this blog) is released under the GNU GPL license. So is phpBB, the board software used to run BOB. The essential purpose of the GPL license is to provide software authors the rights of copyright and to provide software users with the freedom to do whatever they want to with the software. There is a FAQ provided by the FSF (Free Software Foundation) that addresses many questions related to the GPL but I would like to call attention only to a few specific items.

I want to get credit for my work. I want people to know what I wrote. Can I still get credit if I use the GPL?
You can certainly get credit for the work. Part of releasing a program under the GPL is writing a copyright notice in your own name (assuming you are the copyright holder). The GPL requires all copies to carry an appropriate copyright notice.

Simply put, this means that even though I am releasing code under the GPL I still retain the copyright to the code. Releasing it under the GPL ensures that anyone who downloads the code for use has the right to do so, and that those rights cannot be removed by someone else. If someone were to download my code and modify or improve it in some way, then the modified / improved version must also be released under the GPL, so that everyone can benefit.

If I add a module to a GPL-covered program, do I have to use the GPL as the license for my module?
The GPL says that the whole combined program has to be released under the GPL. So your module has to be available for use under the GPL.

That restates what I was saying earlier. By releasing my code under the GPL it protects everyone. Someone could take my program and turn around and try to sell it, but anyone who buys a copy – even if there are improvements – has the right to then distribute the software for free. Code based on GPL software must be licensed under the GPL, which grants the user the right to decide what to do with it, not the owner of the copyright.

What does this have to do with anything? :) I just finished a project where I reworked a very large universe. During that project I used my universe comparison tool quite extensively, and I think the final testing is done. I will be posting a copy of the VBA code for download next week here on my blog. The software will include the GNU GPL license so that anyone is free to use it in any way they see fit.

Keep in mind that – unfortunately – there is already an expiration date on the software, as the BI 4.0 Information Design Tool does not initially ship with an SDK, and even when it does start to provide one it will likely be in java rather than visual basic. So enjoy it while it lasts. 8-)