Most of Android partitions are mounted as read only.
For eg. /system where most of the libs and other system components are stored, including the permissions.xml file.
You can temporary re-mount the /system partition to read write and load your new files to that partition!
using adb shell or the android terminal with root privileges, do the following:
See the currently mounted partitions:
Then re-mount to read-write the partition you are interested in , eg. /system:
# mount -o rw,remount -t yaffs2 /dev/block/mtdblock3
# chmod 777 /system
You can also:
mount -o rw,remount -t rootfs /
Now you can write on the Android read-only file system. Sweet!