Hey Daniel,
You can actually install Easyblog in multiple domain site without any issue, the only issue is other domain sites unable to retrieve the Easyblog latest version info, it will not cause other issue.
However, if you purchase PRO license only entitles you to support for 1 domain only.
If those domain site which required more support from us, I would suggest you set that domain site to your dashboard
https://stackideas.com/dashboard
And If you require support for additional domains, I would recommended you upgrade your PRO license to developer license so you can entities support for 5 domains site.
Hope this will help.