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I am developing a commercial application. There are several programs under GPL which have some common features with my planned applications.

Can I take ideas from those applications under GPL and implement them myself without copying the code?

Would this violate the GPL?

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if the code is open, the idea would be too. did you read the license text? does it say anything otherwise? is it a standard text? –  tgkprog Apr 27 '13 at 12:33
    
@tgkprog The line which says about writing the same code in a different language, caused a bit confusion, if I peek through the code and then write everything from scratch, will it violate GPL making sure the codes are as different as possible. –  adnan kamili Apr 27 '13 at 16:49
    
Taking an idea does not violate anyone's copyright, however if you copy the code, even if you then modify it, you will need to abide by the license under which the code is published. I don't think you'll get a good answer to your question unless you expand it to explain what you are trying to do. For example, why are you unwilling to license your work under the GPL? –  Dominic Cronin Apr 27 '13 at 19:51
    
@DominicCronin There are many possible reasons why someone doesn't want to use the GPL, earning money, ... . The interesting part is how taking ideas actually works? With code under GPL I can actually look into it and take ideas even from the most fundamental level. So where is the limit there? That is the interesting question. –  Trilarion Jun 9 at 13:36

1 Answer 1

up vote 7 down vote accepted

Short answer: Ideas, yes. Source code, no.

The source code is protected by copyright and the license only allows you to use the source code if you license the result as GPL. This doesn't block you from selling the result, but requires you to provide the source code to anyone you have sold the application to (and stops you from barring them passing the source or app on).

The ideas should be OK, as long as they're not otherwise protected (patents, essentially). There may be patents that allow an automatic license only for open source.

As always, please consult with a lawyer before taking legal advice from the internet. I am not one, so this is pure layman advice.

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you mean finance apps that use open src or any other company application like face book or win amp - > has to make their complete source core as open cause they use open source + their own ? –  tgkprog Apr 27 '13 at 17:10
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@tgkprog No, there are permissive open source licenses that don't require that. The question is about the GPL though, which is a "viral" license. –  Brian Marshall Apr 27 '13 at 19:45
    
haha nice history there. A cancer if you allow it ! –  tgkprog Apr 27 '13 at 21:55
    
There is probably a very thin and hard to define border where ideas end and source code starts. –  Trilarion Jun 9 at 13:32
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@tgkprog A website (like Facebook) can use GPL code all it wants without having to license anything under GPL as long as it is all server-sided. The GPL only forces you to open source your program to those people who receive copies of said program. When it all runs on your own servers, you aren't distributing it, so you can keep it to yourself. There is the AGPL license which closes this loophole, but there aren't many projects which use it. –  Philipp Jun 9 at 21:42

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