/storage/emulated/0 is read only and when I try to copy (also when I try to move) files from it to my real SD card, I get a 'read-only' error. I have a Samsung Galaxy Mega with Jelly Bean 4.2.2 and I get this failure with four different file management apps, and also when trying to add the files into a Zip archive.
Well, after much testing, found the destination MicroSD card had file structure corruption, causing the problem. It was resolved by mounting the MicroSD card on a PC, copying all the good files to a desktop folder, running gparted to unmount and reformat the MicroSD card, and copy the files back once the formatting completed.
Rooting was not required to access /storage/emulated/0 .