1. There is X-Win for the Amiga,A AmiWin,DaggeX and the one in
the alpha-tree off the Geekgadgets. None of them is really usable
on a 68k-CPU, and that is why none off them has been maintained
for the last years (+ other reasons).
2. There is even a linker-lib that emulates X11-functions in
standard Intuition-windows, but that is also dated and buggy.
3. AbiWord uses GTK, which itself is not platform-dependant,
"all" you would need to do is port the GDK and the clib which GTK
relies on. Still much work, but no comparison to the gigantic
task of porting OpenOffice. But AbuWord is also no match for OO.