GPL - Do I have to distribute the source of my changes?
<p>I will be creating a piece of (probably) commercial closed source software. It will be a web game. I hope to use some software that is GPL licensed, like nodejs or express(js). If I make minor changes to these frameworks, mostly to change a small behaviour I do not like, do I have to publish that change? Also can I include unchanged software in my project?</p>

<p>None of this is being distributed, it will only serve pages to clients.</p>

<p>If the software runs entirely on <em>your</em> server, it is not generally considered to be "distributed" (for GPL v2) and is certainly not "conveyed" (for GPL v3). That excuses you from all GPL requirements. There is a different license (the Affero GPL) which does apply to use on your own server communicating with others, but that was written precisely because the GPL does <em>not</em> apply. </p>

<p>This is the interpretation adopted by the FSF, who wrote the GPL. See their answer to this question <a href="http://www.gnu.org/licenses/gpl-faq.en.html#UnreleasedMods" rel="nofollow">here</a>. </p>

gpl