The purpose of Flip4Mac is to play as many types of WMV on your Mac as possible. Since Microsoft implemented Silverlight you must have it for media wrapped in that player. Without it, a whole bunch of folks may start complaining," Flip4Mac can't play . . ." Silverlight ensures that you'll play those files since Flip4Mac can't. NetFlix instant view is a good example.

and . . .

You CAN create Silverlight with Flip4Mac.
Once your file is in Quicktime 7.x Pro (must be Pro)
File>Export>
In the Save Exported File As box
Export to Windows Media
Click on Options
You'll see four tabs
Video, Audio, Content, Silverlight

The Silverlight tab allows you create a WMV wrapped in Silverlight
just as one might create an FLV in a Flash Player.