How do licenses such as GPL regard copying of code? [closed]

Question

I understand it's best to implement other libraries where possible (rather than copying code), but in some cases, it's more convenient to copy code.

What is the correct etiquette for copying code? Credit at the top of your file, near the code used? What if the code is re-factored beyond recognition?

Answer 1

The GNU GPL is very specific about how you may use the code you obtained through that license. (Be careful: If your license to the code in question is not GPL, but for example LGPL, different rules apply.) Basically GPL boils down to this:

• If you keep the code for yourself and don't redistribute it to anybody else, you can do whatever you want with it without any obligations.
• If you plan to share your code with somebody else, you are only allowed to do so under the GPL license. This includes that you provide the complete source code with your distribution (including your own code!), that you clearly state to the other party that this code is licensed to them under the GPL (including your own code!) and give complete information on how you altered the original code.

Even if the code is re-factored beyond recognition: If you want to distribute it, you have to follow these terms and make it understandable to the other party which parts you changed (beyond recognition ;-)). Be sure to not forget: This is not etiquette, this is copyright law!

Other licenses, such as the BSD licenses, have different terms. For example, if you use code under the BSD license, you only have to keep the copyright statement, but may happily redistribute the code under any license you like to choose, with source code or not.