You must offer some examples of bad translation, those that speak norwegian could see if the translation is so bad as you say it.
But more generally, if you are not happy with the translation of a program, you can correct the existing translation or make one from scratch. After finishing and testing your translation, you could post it in the forum as an alternative translation to the one included in the software.
For FDM you have instructions on how to translate in this thread:
http://www.freedownloadmanager.org/boar ... php?t=6681