Well, the Palm native SDK has been released today, and yes, it is indeed a codesourcery toolchain + a patched SDL for OpenGL ES support (not unlike the SDL_gles extensions I released a few days ago to extras-devel...)
Instead of, say, (like on SDL_gles) a Palm native SDK developer would have to . I could change my extension to resemble that easily... (rest is mostly the same).

• Keyboard events go through the usual way.
• Single finger touchscreen events are sent via mouse events (like on the N900), multi finger touchscreen events are sent via "multiple mice" events.
• Gestures in the gesture area via virtual keyboard events.
• Accelerometer is read via the sdl joystick interface (like on the N900 with accelemymote).
• Sound is handled via the Pulseaudio SDL driver (and SDL_mixer) -- like on the N900.
• They have written a very simple SDL binding for some media player framework (gstreamer, I suppose): SDL_cinema. The wrapper is very simple (too much IMO).
• They have a new SDL event type for their OS stuff, like the above library's end-of-stream event.
• They also have an extra library for OS stuff: preventing the screen autodimming (Nokia has this already in hildon-games-wrapper), changing/detecting the device orientation, enabling the gesture area, their own equivalent of Maemo's liblocation, etc.

So, source compatibility can be attained with a few one-line preprocessor macros . Let's see about binary compatibility.