The Free Software Foundation has long been one of those outfits that has refused to accept (significant) source contributions without the author signing a “Contributor Licence Agreement”. It’s not enough to release the code under the same licence as the project, you must also hand over the entire copyright to them. This is supposedly because they have received legal advice that it makes it easier to defend against copyright infringements if they own all the code. Quite a few other projects don’t agree <https://lwn.net/Articles/592503/>. For example, the Linux kernel project does not demand CLAs, only a “Certificate of Origin” (affirming that you have the right to contribute the code). And now the GNU Compiler Collection is joining them. <https://www.theregister.com/2021/06/02/gcc_fsf_code_copyright/>