Plain gdb and insight (that is the GUI extended gdb) can be built with
just one build: download insight-5.3 instead of gdb-5.3. Then apply both,
gdb-5.3-bdm-683xx-patch and insight-5.3-bdm-683xx-patch. This builds
m68k-bdm-coff-gdb (this is plain gdb) and m68k-bdm-coff-insight (this is
GUI-enabled gdb)

To get insight running I needed to put the following into my .gdbinit68 file:

  set prompt (gdb-bdm) 
  set hash 1
  bdm_log off
  bdm_setdelay 0
  bdm_autoreset on
  bdm_timetocomeup 0
  bdm_load_use_lma 1
  #target bdm /dev/pd_bdm0
  target bdm /dev/icd_bdm0
  bdm_debug_driver 0

  # this macro is called by insight directly after attaching to target but
  # just before the processor is let to run.
  #
  define reset
    bdm_reset
    bdm_entry gdb_entry
    set $pc = gdb_entry
    set $vbr = __s_text
    set $sp = ((unsigned long *)$vbr)[0]
    #
    # insert breakpoints on positions that indicate big trouble.
    #
    delete
    break excpt_handl
    break halt_system
    break uninit_irq
  end

There is still a problem with insight: On start up insight sometimes get
into an endless loop trying to read a cycle of stack frames. I don't know
what triggers this loop, but when it happens once it is perfectly
reproducable. Deleting ~/.gdbtkinit helps in this case, but I have no idea
why it helps.