Good question.
With version 3.0.2.0, the launch page sniffs the client configuration and selects the single installation technology best suited for that client. Assuming you've checked all of the download technologies available, the selection goes as follows:
For Internet Explorer:
|1) If the ActiveX control is already installed, use it
2) Otherwise, if the .NET Framework 2.0 is installed, use ClickOnce
3) Otherwise, if java 1.1 is installed, use java web start
4) Otherwise install the ActiveX control and use it
For Mozilla:
1) If the plugin is already installed, use it
2) Otherwise, if java 1.1 is installed, use java web start
3) Otherwise, install the plugin and use it
Version 3.0.3.0 (currently available as a beta, but soon to be released) works the same way, except that it includes links to the the other technologies in case the default selection doesn't work for some reason. For example, let's say the default selection for a Mozilla user is java web start. That user will also see a small link at the bottom enabling them to try the mozilla plugin. Internet Explorer users will see a link to try the ActiveX control. This gives participants a backup option if the default doesn't work.
Regards,
Sean