VP3 is a symmetrical algorithm meaning that it can compress at the same speed as it decompresses i.e. realtime, making it more useful for live streaming than DivX (of course eventually DivX will become compressable in realtime with beefy processors, making it usable for live stuff). There's obviously a quality difference, but that's why.
NSV is only a container format, it can use any format for audio/video, and so DivX could be added.
For long you live and high you fly, but only if you ride the tide, and balanced on the biggest wave you race towards an early grave.