The only official site for buying Pro is Official Website & Free Download - Lime Wire
You're only able to download Pro versions while your benefits are current (depending on whether you buy Pro for 6 or 12 months)

The official site has no facility for editing your email details - you just buy Pro & enter your current email addy in the purchase details. Your email address will stay in the database until your Pro benefits expire.

The current version of LW is 5.4.6. You'll find it's really different to LW 4 versions. I'd suggest that you try the free basic LW first, to see whether you like it
Here's a link to the changelog, so you can see what changes have been made since 4.14.10: http://wiki.limewire.org/index.php?title=Changelog

If you do want to buy Pro again then go to the first link above & click on Product Features... now you'll see the option to buy Pro for 6 or 12 months. Sometimes there's the option for a one-off download (only able to download the installer once & no email support) but that doesn't seem to be there at the moment.