It is possible to have more than 1 input but you need to delve into Quicktime a little.
Excuse me but i cant remember the detail but it was something like you have to make a quicktime movie using an input component and then import it as a media file into Modul8.
This link may help
http://developer.apple.com/DOCUMENTATION/quicktime/RM/ImportExport/DataExchange/F-Chapter/chapter_6_section_13.html
It is not possible to input a vga signal into Modul8, you'll have to convert it to a video signal via a scan converter if your source doesn't have video output.
There could also be issues with using 2 firewire inputs at the same time so you may have to get a USB capture device for the 2nd source.