No worries. If you register again, using the same email, you will get the exact same activation key. So then you have it again.
Also, if you change computers, Animation Paper will let you run on the new one using the same activation key. You can change computers all you want, but the old installs will eventually stop working. So it’s pretty free and easy.
Your account on this website that you use when posting on this forum, is a separate thing and not related at all to your Animation Paper license.
The .ap files you may produce is simply .ap files. No “ownership” or anything. They are fully interchangeable – also between Windows, Mac and Linux versions and even with the iPad and Android versions, when we get them done eventually.
I hope this clears matters up a little. Otherwise let me know 😉
Thanks,
Niels