Question about beta invites

Hi all, my first post.
I joined in the last public beta weekend, and liked the game (or at least what I could play of it).

My question is this, if I donate and get a closed beta key, can I invite a friend of mine to the game?

How do beta invites work? Who got them?

I think it goes as if you buy 1 key, then your friend would have to purchase/win a key/access themselves. But if you buy a higher tier package with multiple keys you can pass one along to a friend or multiple keys to different people!