Very great contribution.
It works fine with GUIs compiled with 2008b (compiler v79).
The file matgui.exe might not work as with newer version of the compiler it is given with mclmcrrt79 instead of mclmcrrt78 (so that file is then missing to launch matgui).
Fortunately, the splash screen doesn't care about that ;)
Would you consider supporting bitmaps bigger than 320x160 ?