For cd burning software, the software maker sells it very cheap to the cd-rw drive manufacturer to let them bundle it with their drive as a selling point and also help the software maker to spread their software, the drive manufacturer cannot sell this software to someone else alone. Don't you always see something like "this software is for bundle with this hardware only, not for resale" on the cd?
For oem hardware, the manufacturer sells it very cheap too, the requirement is to bundle it with system or other hardware, they don't want the distributor, wholesaler and reseller/retailer to sell it alone, that'll affect their retail channel sales. Like the MS intellimouse optical, retail msrp is $45, oem version (just the mouse, no retail box) from online vendors is just $20 (supposed to buy with other hardware).
Back to this deal, this reseller got some nero oem version from either grey market or taken from other cd-rw drives, this Nero could be a cd-rw drive specified version, so they give you another serial number to make it workable on any drive, isn't this same as you download Nero demo version and use a key generator from warez site? This CD is legit but the way the reseller aquired it and sell it is not legit, you buy such version software doesn't help the software industry, you're helping the computer grey market only.