Sure! You don't need to be an eBay seller to sign up.
When signing up all we need is that you will provide us with an email and name, in addition to a PayPal email we can send your affiliate payments to. For more information visit this link:
https://www.3dsellers.com/3dsellers-referral-program.
Let me know if you have any other questions.
Sincerely,
Tzipi