Limewire has been shutdown under a court order, as mentioned on their official website.
Limewire Pro has also been discontinued as a result, so if you see any website selling this product, it's a scam.
There is a custom version of Limewire called "Limewire Pirate Edition" created by a small group of developers. This is freely available, which is distributed via BitTorrent and there is no charge for this.
Basically, if you see any website claiming to sell Limewire (pro, 2010, 2011, etc.) it's a scam!