Finally getting back to this. Compiled tn5250 from cvs:
$ tn5250 +version
Ran configure then make on x5250 and got errors on make:
x5250term.c: In function ?x5250_terminal_waitevent?:
x5250term.c:1840: warning: passing argument 1 of ?XRefreshKeyboardMapping? from incompatible pointer type
gcc -DDATADIR=\"/usr/local/share\" -g -O2 -o x5250 -l5250 alloccolors.o debug.o dialog.o help.o mouse.o key.o resources.o x5250.o x5250term.o -lSM -lICE -lX11 -lXext
mouse.o: In function `buttonreleasehandler':
/usr/local/src/x5250-0.5.2-pre4/src/mouse.c:776: undefined reference to `tn5250_window_list_find_by_id'
/usr/local/src/x5250-0.5.2-pre4/src/mouse.c:800: undefined reference to `tn5250_window_list_find_by_id'