Yes, it's normal. The disc check in built into the Fallout launcher, and FOSE_loader.exe has to bypass that in order to work. I've kept my DVD in its protective case for most of the time I've owned the game, only taking it out when I absolutely needed the disc (reinstall the game, new video card, etc). Pretty sure this is intended functionality, it works without FOSE if you just run Fallout.exe.