GNU General Public License

hhajar2002 · April 13, 2013

Hi,

I studied a document about GPL license which talked about making money from open source software under GPL license, It said that we can charge fee for both program and code, but there is a limitation for the amount of money we receive for source code. does any one know how much is the maximum amount we can rcieve for the source code of zotero?

dstillman · April 13, 2013

Could you elaborate on what you're trying to do? The answer somewhat depends on how you're distributing the program/code.

I believe what you're referring to is the requirement that, if you distribute binary-only versions for a fee, you also make the source code available at the same time or upon request without a further fee, since otherwise you could charge a billion dollars for the source code, making it effectively closed source.

Also, anyone who purchases a copy from you is legally able to distribute it without charge, including your modified source code.

mronkko · April 13, 2013

There are a lot of misconceptions about the GPL license. The "problem" is that when you sell someone a GPL license, you give them the right to relicense the work so any of your customer could become your competitor.

http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLAllowMoney

Selling GPL licenses is not a viable business model. Selling services for GPL licensed software or dual licensing is.

hhajar2002 · April 17, 2013

What if I charge a low amount for source code that I have made changes in? I know that GPL doesn't let me to charge for a billion dollar for source code but it lets me to charge it for a limited amount. I want to know this limit for zotero (for instance zotero can tell me you are allowed to charge the source code up to 100 dollars). I exactly wanna know this amount.

fbennett · April 17, 2013

@hhajar2002: Follow the link provided by mronkko; it answers your question.

The answer is also given by Dan and mronkko above: you can charge any price you like, but if you sell your program in binary form, you must supply the source code for no additional charge. In either case, you cannot prevent others from modifying or redistributing the code. So there is no limit, but if the price is high, you will be undercut by others who build on your work (or not) and sell for less. Under the GPL, the software trade essentially becomes a service business, as mronkko says.