each link has an invite code in it

http://seed4.me/users/register/ca4fcf16-ffff-4f1b-9945-cd0bf818296d

http://seed4.me/users/register/c2e66fc7-689c-49a7-bd59-270fd16a172d

http://seed4.me/users/register/50e9c63e-af8e-4b82-b959-5bcedf392789