But you can. What the GPL says is that if you distribute/sell the object code, you must distribute the source code as well. So you have no obligation to distribute anything to anyone, but if you do distribute the code, you are obliged to distribute the source.<p>Quoting from Stallman's <i>The Free Software Definition</i>:<p>You should also have the freedom to make modifications and use them privately in your own work or play, without even mentioning that they exist. If you do publish your changes, you should not be required to notify anyone in particular, or in any particular way.<p><a href="http://www.fsf.org/licensing/essays/free-sw.html" rel="nofollow">http://www.fsf.org/licensing/essays/free-sw.html</a>