it is not that ts_open is missing but ts_calibrate wants to open a device that does not exist.
ensure that your TSLIB_DEVICE is set
I think that once I can figure out which device TSLIB_DEVICE needs to be set to, this might work. In fact, I got somewhere by setting TSLIB_TSDEVICE="/dev/input/mice" and others. I have:
Zaurus:/afterinstall# ls -la /dev/input
total 0
drwxr-xr-x 4 root root 220 Nov 9 15:44 .
drwxr-xr-x 13 root root 2980 Nov 9 16:07 ..
drwxr-xr-x 2 root root 80 Nov 9 15:44 by-id
drwxr-xr-x 2 root root 140 Nov 9 15:44 by-path
crw-rw---- 1 root root 13, 64 Nov 9 15:37 event0
crw-rw---- 1 root root 13, 65 Nov 9 15:37 event1
crw-rw---- 1 root root 13, 66 Nov 9 15:44 event2
crw-rw---- 1 root root 13, 63 Nov 9 15:37 mice
crw-rw---- 1 root root 13, 32 Nov 9 15:37 mouse0
crw-rw---- 1 root root 13, 33 Nov 9 15:44 mouse1
crw-rw---- 1 root root 10, 223 Nov 9 15:38 uinput
and, with some of them, I get a touchscreen calibration screen. But, it always says that the calibration failed.