I've sent message with the same subject to users list. The languages list containing percentage values of translated items was generated with shell script:
#!/bin/bash
ENCOUNT=grep -e '^\\$' en_US/* | wc -l
for x in ls -1 | grep -e '^[a-zA-Z_]*$'
do
COUNT=grep -e '^\\$' ${x}/* | wc -l
DIFF=$((ENCOUNT-COUNT))
PERCENT=echo "scale=2; $COUNT * 100 / $ENCOUNT" | bc
echo "$x: $PERCENT% ($DIFF)"
done
It would be nice to have something like that somewhere on roundcube webpage.