1.) Does anyone have any experience with GDDM graphics? (I searched the mailing list archives and found nothing.)
lib5250 doesn't support any sort of graphics at this point. xt5250 will never support them, since it's a curses based (text-only console mode) emulator. There's no way to draw graphics in that environment.
However, x5250 and the Windows port may support GDDM graphics some day. It doesn't support them today, however.
2.) Which system/software is the issue: a.) Stream from AS400? b.) tn5250? c.) Linux or more specifically "X"?
tn5250. (or more specifically, lib5250)