DISCLAIMER: The topic, content, and arguments of this article may be sensitive to some peoples. Any arguments written below only applicable to my GPL software, it may not applicable to all software released under GPL.
When I publish my first software to the public, I choose BSD like license, for the following reasons: it is free and open source (FOSS) license, easy to read and understand, and simple. There are others license that are simple and short too, of course, like Expat (MIT) license; but I did not choose it for the reason that BSD is enough. That is the first license that I use through of my all my free software.
After ten years, I never thought about it. I had changes the license format once, from 4-clauses to 3-clauses, removing the "advertising material" clause, and that was it. Couple of weeks ago, I began thinking and research about GPL, and finally decide to changes the license of my free software.
This article does not try to compare between free and open source licenses, there are too many of them, but to understand my inner thoughts on why I finally choose GPL.
What do you think about (BSD and GPL) license?
FOSS license is a unsigned, social contract between me, the copyright holder, and you as the user that receive a copy of my software.
Under BSD license, you can copy and do whatever you want with the software, in other words no one care. As long as you retain the copyright holder, you can sell it, changes it, and/or make it proprietary. That is the line that BSD license draw between you and me, the copyright holder. Nothing I can do about it.
Under the GPL my software is guaranteed to be free!
If someone copy my software, if something happened to me (even if no one use my software), my software is guaranteed to be free. Of course, I will not know who and what people do to my software. You can copy it, modify it, remove copyright holders, and publish it under different name, commercialized or not like what you did with software under BSD license. It is not my obligation to tell you what to do with my software, but under GPL, it is up to your conscience. If you redistribute your changes, that means you giving back to community.
This is the line I want to draw with my software and where I stand and want to be in community. I want my software, and any derivates (changes) from it, to be free too. Period.
Why you want your software to be free?
People changes … or bored, hardware changes. In closed source system the changes is either slow or steady depends on the maker resources. If one maker tried to cope up with their ecosystem, other makers who have more resources or better idea can make the same software with a greater look and performance. Eventually one of the maker will die or born again with new skin and body. Just like the circle of life. This is also why human is doomed. Every new born does not automatically have knowledges of their ancestors. They must learn again and again and again. But, machine made everything simple, even learning. Only human that does not learned who will doomed.
If the makers keep doing this, we will just reiterating the same thing again and again, wasting resources for the sake of competition and margin. On one side this is good, giving jobs to the market, making the money flow. But on the scale of future, where human only have an average 60 to 70 years lifespan, this is definitely wasting of resources.
Any program that use your GPL-ed software, now must licensed under GPL too. Is it true?
Yes, if you use it as a library; no, if you use it as a standalone program.
But once again, it is not my obligation to tell you what to do with my software, but under GPL, it is up to your conscience. If you redistribute your changes or licensing your software under GPL that means you giving back to community.
Does that means GPL limiting other freedom to use your software?
The word "freedom" that some people use on when asking this question or questioning that GPL limiting the freedom to use the software is kinda misleading. How come something that I give, limiting other freedom? That does not make sense. Do I force you to use my software? No.
I put peanuts on the table outside the street and write "Free peanuts" on top of it. You know you are allergic to peanut and see the written "Free peanuts", do you still take the peanuts? I am not forcing you or anyone to take the peanuts either.
If all is up to my conscience, what is the point?
Nothing actually.
One of the reason that I use GPL on my software is to say thank you to all GPL software that I use for the last 15 years or more.
Thank you for writing and publish your software under GPL so I can freely use it. I know that you have giving your invaluable time, skills, and patience to write and maintenance those software. As a respecting gesture, here is my software licensed under GPL for you or any one else to use it freely.
It is now up to you, if you use my software (or any GPL software).
Any other reasons beside that?
Vision and community.
If I choose BSD, I am a lone wolf, along with others. There is no a BSD Foundation. Although there is a NetBSD Foundation, FreeBSD Foundation, OpenBSD Foundation, but that is not strictly related to BSD as license.
In GPL, they have one foundation called Free Software Foundation. Anyone who use GPL, either share the same vision with FSF or support GNU (the operating system) which is "to promote computer user freedom".
Of course, this does not mean that someone who create and publish their works using non-copyleft license (like BSD) or proprietary license can not support or join the FSF community. The world is not black-and-white, we play many, different roles in this life.