VB and open system? haahhaha (excuse me) .... so basically your customer wants a complete re-write then? I suggest you look into
Qt library. A multiplatform application devlopment toolkit with database support and a very user friendly and intuitive API. There is a GPL-style version available and various commercial licenses. I've been using it at work for the last 6 months and I must say that I'm quite pleased with it. Trolltech also offers *excellent* support, they have thusfar allways answered all of my questions within a day (and sometimes within a matter of hours).
As for the capturing of a video stream, this is quite easy under linux (did it myself a while back , grab the stream of a webcam and use it as an OpenGL texture) with the video4linux interface.
I'm not a windows programmer so I don't know your options for windows concerning video streams (prolly somewhere in MFC orso, or in directx, but I wouldn't know
)
The videostream code would be heavilly #ifdef'ed tho, which is practically unavoidable when programming for multiple platforms.
Another option is to persuade your customer to wait a year orso till the new GNOME .NET project is matured, which will offer an API similar to MS's .NET, though this is very much in early development stages (look around a bit on
http://www.slashdot.org, there was an article on it a short while back).
hope this helped.
