If you have sites on the same server, assuming site a has the ability to access the inferno external file on site b, then yes.
For instance, if you had a site setup on your server which was infact just a folder on another site, eg:
Your main site was:
mysite.com
Your main forum was:
mysite.com/forums
Another site on your server was:
mysite.com/siteb/ but accessed normally through mysecondsite.com
Technically then your 'mysite.com' could acces both your forums and the other site. All you need is the ability to load the inferno external file and you can display data from that forum at your disposal
- Zero Tolerance