From the FAQ:
Q: What is riplock and do I need it?
A: Riplock is a term used for locking the reading speed on a drive for certain media types. For example a DVD-VIDEO will only read back at a certain speed, somewhere around 4X - 5X. This keeps the film makers happy as you wonâ€™t be able to backup a DVD very quickly. Another use for riplock is keeping noise levels down when playing back a DVD movie on your PC.
In most patched firmwares riplock has been removed, allowing faster rip speeds, these will generally only affect pressed DVD discs. For DVD5 (SL) the drive will generally reach its max read speed with riplock removed. For DVD9 (DL) the rip speed will be much reduced. In the case of the ND-3500 series drives, about 7X is all you should expect.
Riplock removed can make a drive noisier when playing back pressed DVDâ€™s on your PC.
Use NERO Infotool, DVD Identifier or DVDInfo ...
A drive sold by, lets say MadDog, will be identified in your computer as MAD DOG rather than as a NEC. It might also have a stamped MadDog logo on it, and the warranty label will say the unit is a MadDog model 16X9A2 or something like that. In fact the drive is rebranded as MadDog, but inside it is just another ordinary NEC3520! Normally these drives should use the firmware provided by the MadDog, not the one provided by NEC, hence NEC's note.
The meaning of the OEM from a retailer's view point, is that the drive comes bare, without a box, SW, manual, cables, etc ... e.g. is not retail. These ones are identified as NEC, and as such you can update them with NEC FW.
Other manufacturers do make a difference between their retail and OEM drives they sell, and they have two different sets of FW's but normally this is not the case with NEC. Try NEC 3.04 and see if you can update it.