Hm, what happens if you modify /usr/sbin/grml2ram to use "Inactive" instead and
what happens if you drop the check overall?

Because I'm not sure that "Inactive" would really help, example output from one
of my systems:

# grep MemFree /proc/meminfo  
MemFree:         3568244 kB
# grep Inactive: /proc/meminfo
Inactive:        2803648 kB
# free -m
             total       used       free     shared    buffers     cached
Mem:         15784      12357       3426          0       1733       5297
-/+ buffers/cache:       5326      10457
Swap:         2045         94       1951
#