> 1. You're not "giving up" the rights to your contribution, you are sharing the copyright with the organization. That is, your work is your work and you're still free to do whatever you want with it.

Sorry, but - as a general rule, this is false, at least in common law jurisdictions. Copyright is a transferable property right. If I assign copyright on a work to you, I don't have it any more. (That's a bit of a simplification, ignoring moral rights and glossing over more complex situations like if we're joint authors, but the gist is true).

Now, the FSF agreement (and most other CLAs) has a 'grant-back' clause: after you assign them your copyright, they grant to you a wide perpetual licence to use, copy, relicense, etc. etc. the software. So you can still do most[1] of what you could do before.

But that's a function of that clause, not something inherent in assigning copyright.

[1] Most -- but not all. There's one thing that having the copyright lets you do that a licence never can, and that's enforce it against third parties. You can't sue someone for breach of your copyright after you've signed it away, only the copyright owner can, and that ain't you any more.