[Axiom-developer] Re: [Maxima] Re: GCL used commercially?

    This puts it quite clearly.  The GPL is not about defending our work
    (against proprietary forks etc.), it is about constraining others to
    license *their* work under the FSF's preferred terms whenever possible.

The GPL is about protecting our work from misappropriation, and
leveraging our work so that others who wish to incorporate it in their
published programs must make those programs free as well.  (See
http://www.gnu.org/philosophy/pragmatic.html.)

However, it is inaccurate to say that the GPL requires someone to use
"the FSF's preferred terms" for his code; the GPL does not do that.
Your changes do not have to be licensed under the GPL specifically.
They can be released under any GPL-compatible free software license.