I have recently ported rdesktop to the hp touchpad. I based this work on an erlier version of rdesktop (1.5) that was using the SDL library. Basically, I made some semi significant changes to the SDL rendering code, keyboard handing, and integrated a basic wrapper around the command line interface that exists in rdesktop. I also started a rdesktop SDL project on sourceforge.
Frankly, I'm curious, as there have been SDL ports in the past, if there is any interest in having an SDL interface layer in the base rdesktop source base?
If so, I can probably separate the SDL specific code out as a replacement for the X portions and add a makefile/config switch to control the rendering engine. I would just post the code here, but as it is, i've sprinked ifdef WEBOS's pretty liberally through the code base, and I don't imagine anything like that is generally useful. I will be posting the code shortly (there are a couple things I want to fix first...), probably against the rdesktop SDL project.
I have a fair amount of work to do, merging the latest rdesktop changes into it as well... Once that and some connection manager things are done, i'm willing to go after some of the newer RDP v6/7 pieces.