I'm new here in this forum, so I don't know whether this was discussed somewhere else, but last summer I had the same problem and after searching the internet for hours and found nothing, I think there is no way to decode these locked .rmap files (correct me if I'm wrong).
BUT, there is another way, it worked for me very well, but it's time consuming. You simply open the .rmap in compeGPS, zoom to 100%, and go capturing the screen with print screen key, and then stitching the tiles in Photoshop. Once you have the whole map, you save the image, open and calibrate it in compeGPS and save it as open .rmap, or any other format you like.
Hope it helps.