Here's how to get the email invite to link to the CB registration form.
You need to edit this file: components/com_invite/invite.php
Find this bit of code on or around line 170
[code:1]$link = sefRelToAbs($mosConfig_live_site . '/index.php?option=com_invite&task=register&email='.$e_add.'&ref_str='.$ref_str);[/code:1]
replace with:
[code:1]$link = sefRelToAbs($mosConfig_live_site . '/index.php?option=com_comprofiler&task=registers&email='.$e_add.'&ref_str='.$ref_str);[/code:1]
Now the email that is sent as an invite will link to the community builder registration instead of the registration form included with the invite component. There is no tracking
I've been digging through the code and there doesn't seem to be an easy way to get it to track based on the CB registration form.
Also, a better method to verify invitation acceptance is needed. The tracking is not fool proof because most people will want to browse around before signing up and then their invite will not be validated unless they go back to the page that was linked to from their email invite. If I could write a plugin for this I would, but it is over my head.