If you want Superuser whitelist app on mustymod rom, read this post.
xda-developers - View Single Post - AOSP 2.0.1 for HTC Hero
or just get the zip file, unzip it and do the following:
adb push su /system/xbin/su
adb shell chmod 4755 /system/xbin/su
adb push Superuser.apk /system/app/
adb shell sync
Also, if you want all busybox love from the shell, just do the following:
#su
#cd /system/xbin/
#./busybox --install .
Don't forget the dot at the end.