Sorry, no nice install script yet (and the sources are a bit messy...).

Now to install BeSANE you have to:

copy sanei/libsane.so to /boot/home/config/lib/

copy the drivers from the dir backend to /boot/home/config/add-ons/SANE/
copy the config files(they have the same name of the driver with the .conf extension) from the dir backend to /boot/home/config/settings/SANE/

finally, for USB support, copy the driver in BeOS/usb_scanner to /boot/home/config/add-ons/drivers/kernel/bin/
and create a link to this driver in /boot/home/config/add-ons/drivers/kernel/dev/scanner/usb/ 

Now you can scan using frontend/scanimage from the Terminal, docs are available in the doc dir.

Please, mail bug reports back to besane@intuiware.com