So far, I added all the missing paths to PATH
(export PATH=$PATH:/opt/maemo/usr/sbin:/sbin:/usr/sbin)
EDIT: add the above to $HOME/.profile to make the path permanent

Now, I can successfully issue
airmon-ng start wlan0 (starts monitor device on mon0)

I can also start airodump-ng, but with the same time issue as hoggerz)

trying to start aireplay-ng or airodump-ng on mon0 after airmon-ng outputs

ioctl($IOCSIFFLAGS)failed: Cannot assign requested address

Also, confirms injection is not available when issuing airodump-ng wlan0 with mon0 devoice up

EDIT: we have wl1271, not wl1251 as the N900, so the drivers from David will probably not work directly compiled.
EDIT: Yes, indeed, should do it if we can recompile on the (openmode) kernel, fromDavids Blog "many ports of missing features from wl12xx/wl1271 to current wl1251 (e.g. bluetooth coexistence, hardware filtering, multicast filtering, ...)"

EDIT: For porting the driver, this is very useful: http://wireless.kernel.org/en/users/Drivers/wl12xx
(our kernel is 2.6.32)