If you ask me, the risks (as well as level of safety) are the same anyway. I made a lot of mistakes before I finally got it right (and hence came up with the video tutorial), but it's not really that hazardous, i.e. an incorrect installation doesn't wipe out any data.

After install, I don't see any risks or tendency for it to be unsafe if installed to the internaly storage/memory. Remember that NITDroid dual-boots with Maemo, so meaning to say they will not run both at the same time (same as when you dual-boot your laptop/desktop computer).