You don't even have to get the pro version.
There are different Gnutella Clients out there, some of them free.
You can get a list in the "How to get in" scetion of Gnutella For Users:
http://gnufu.net
As a shorthand here are some:
Open Source
»LimeWire (
http://limewire.com ) - A Cross-Platform Java Client, GPL, shareware.
»Phex (
http://phex.kouk.de ) - Another Cross-Platform Java Client, but with fewer developers and freeware, GPL.
»Gnucleus (
http://www.gnucleus.com/ ) - A LGPL Client for Windows COM-based
»Gtk-Gnutella (
http://gtk-gnutella.sf.net/ ) - A GPLed-client for Linux
Closed Source
»Acquisition (
http://acquisitionx.com ) - A Mac OS X client based on the limewire core, written in cocoa, shareware. (and a personal fave!)
»Bearshare (
http://bearshare.com ) - A closed source Windows Client.