GPL as a way of control

Sun's release of Java with the GNU Public License got me thinking about it. It is subtly powerful to use the GPL.

When there is an active maintainer, (this is key), the GPL allows the maintainer, let's say, Sun, to stay "on top".

Let's say a competitor takes the Java source code, and modifies it to make it better. By the GPL, the competitor must release the changed source code under the GPL, and Sun's active maintainer can merge the improvements back into the original source.

Thus, Sun can always claim to have "the best" (assuming a linear measure of what is good) Java, unless a competitor decides to build the whole thing from scratch.

Maybe if the software distribution is partly being used as a name-recognition or other advertising program, the world will always keep going to (say) java.sun.com to download the best version of Java.