This is particularly dangerous because in the anglosphere, open source licenses are by default bare licenses -- they do not have the force of contract, meaning they can be revoked at any time. An organization which released any code under the GPL or any open source license can revoke the right to use that code on a whim (yes, the GPL'd code itself, not future revisions of that code), meaning a hostile FSF can prevent use, distribution, or -- critically -- forking of Emacs.
Projects such as Linux without a CLA requirement are better protected against this because of their patchwork ownership. A single contributor has less to gain, and more to lose, by revoking their license to their contributions. That's not to say it's perfect protection but it does help.