Hi Mark
Unfortunately there has never been a life time membership for Limewire...There was only ever a 6 month membership and then if you wanted continued support and newer versions you would have to re-purchase at a discounted price...
Recently they have brought in an extended membership of 12 months..
This is the official site....
Lime Wire » Download LimeWire
If you want to transfer your existing Pro version onto your new computer, back up the limewire installer onto an external drive or disk and transfer it that way...