Xinput isnt the one available here: ftp://ftp.x.org/contrib/utilities/ The source is available here now, updated: http://xorg.freedesktop.org/archive/individual/app/ last release 15th of Jan 2009. I dont know how useful it is though.
I wan't aware that there was an old xinput too. So whatever was true about the old xinput, it's probably not true anymore. I've learned about xinput from the http://planet.freedesktop.org agregator, latest entry is from Peter Hutterer (http://who-t.blogspot.com/2009/01/tip-of-day-wheel-emulation.html). So, basically, the xinput utility is the only way to query the X servers input devices, list and change their properties. It also seems to be used for the MPX functionallity (slowly entering in the upstream xorg). -- damjan