2
Just an idea but...
There's an option to 'turn off' your site in Admin>System>Preferences>General
You can specify what groups can access your site while it's turned off.
If you allowed registered users and webmasters only to access your site, that may work.
Then just email the registration link to
http://www.yoursite.com/user.php to your users you want to invite.
Problems:
i) Users may not be able to access user.php before registration.
ii) Anonymous users may be able to access user.php without an invitation.
It's just a thought, there's definately other ways too.
D.
みんなちがってみんないい。
XOOPS 2.0.13.2