I can confirm that this works fine on Vbulletin 3.6.

Yes, this works fine on vBulletin 3.6. That is now official.

This is great but needs to be incorporated within the registration process, so after the user registers, it redirects them to invite your friends page where there is a simple:

MSN Username
MSN Password

Aim Username
Aim Password

Yahoo Username
Yahoo Password

....and so on, with then ONE button that says invite, this would then login in, and send a pre-defined e-mail to all contacts on that users list e.g.
This would then work very well, the fact that the user has to check/un-check, write the message themselves etc puts them off, big sites like Hi5 etc did exactly what is written in my spec above.

The commercial version supports msn contact grabbing, more grabbers are going to be added in future.

Is it possible to also allow the option of simply generating a code, so the user can copy and paste it to the person they're inviting rather than emailing it to them?

Please post that as a feature request at visionscripts (given that you have version 1.5.0 and up).

Eh, I coded it in myself.

Could not read all 42 pages but

1. Is there a port for vBulletin 3.6.0?
2. If this is now a commercial version, do vB owners need to buy a separate license from VisionScripts for $35? I see the download link though.

It's confirmed as working for 3.6 about two pages back :)

Yes. The latest version (commercial) is available with 3.6.0. The free version should work with 3.6.0 without a port.

The version available here is a fully functional free version, but versions 1.5.0 and above are commercial and have more features.