Hi there Jatila,
Thanks for reaching out to us on this!
do I have to purchase it again for my other website?
Depending on the type of license you hold. Personal license will work just for one site, but I see you have a business license which can be used in upto 3 sites. So in this case you can use the same license in two more websites. Just download the plugin from your account on our site, install it in the new site alongside The Events Calendar and input the same license in ‘WP-Admin > Events > Settings > Licenses’ and that should be it.
Please let me know if you need further assistance on this,
Best,
Nico