As an alternative, I strongly recommend Sustainable Softworks' USBPegasusEthernet 1.0.6 driver (or later). It's been tested and works under OS X 10.4.6.
If you're still interested in the older driver, see below.
Based on Daniel Sumorok's Mac OS X 10.3 driver, this version has been ported to Mac OS X 10.4 ("Tiger") and extended to list explicitly the devices which are supported.
To install, just copy the .kext file to /System/Library/Extensions.
Known Bugs: USB hot-unplug is not yet stable.
The source code is freely downloadable, modifiable, and redistributable under the GPL license.
Copyright (C) 2005 Ben Gertzfield, Daniel Sumorok.