This page carries links to other useful information on the Wyse WT3125SE. If you know if other useful resources please let me know.
[Checking in December 2014 the following site and pdf had vanished]
"vt" pointed me at http://evilx99.ev.funpic.de/ which had information on various thin clients. In particular there was a pdf file "Wyse%203125.pdf" describing how to run Debian on the WT3125SE:
Erfolgloser Versuch einer Debian
Installation auf einem Wyse 3125SE
Thin ClientEvil
4. Marz 2010
As you can see it is a German site.