There is a telnet server and utils addons that provides a command shell (ASH). Wyse do not publicly post there (no idea why) but these would do the job. Also if you know where the files are you want to change you can use Rapport to send them.
The Wyse Linux uses Red Hat 9 as a base with the 2.6x kernel and Busy Box.
Ping Wyse and see if you can get the shell, I may be able to dig up some more info on the distro,