Shoutbox

Is there anybody here who know how can I develop something like Messenger Plus!?

I've few more questions

1) is there any different between developing for windows messenger and MSN messenger?

2) where do I start?

3) can I develop in VB.net?

4) what can /can't I develop? is there any limit?

5) is it legal?let's say I'll develop something amazing and I'll sell it to million customers , will microsoft sue me?

THANKS A LOT!!!
Ohad