No the AI functions are built into the full version of Cubase, I use them on an occasion with some Yamaha hardware, mostly KX controllers, I had some problems installing them on v6.5 now that you mention it, I am going to install the extensions again on C6.5 and see what happens … perhaps there is something not obvious going on
Ah … Now I remembered one thing, permission, worth a try, if you are using VistaWin or higher run the installer in administrator mode and run cubase also in administrator mode for the first time after you install.