Based on the Internet Archive[0] + Google, the correct link is: http://www.nationaldatamux.com/lantronix/usfiles.html

"United States Software, Inc. a wholly owned subsidiary of Lantronix, Inc." ... now apparently owned by NDM Networks, Inc.

[0] https://web.archive.org/web/20010429175811/http://www.ussw.c...

Actually, it is (1999):

> This code is an original work by Paul Stoffregen, written in December 1999

The 2005 update just applied minor changes for a new board revision:

> Status: This page is complete, code updated for rev 5 board, January 2005

I found a company called US Software Ltd, but they appear to be an app house in Bangladesh.

http://www.ussoftwareltd.com/

I'm suspecting that 12 year old drive controller code is just no longer available for sale.