Running OS 8.1, with the Apple CD/DVD Driver, a DVD-ROM drive certainly can be used for data storage. Obviously, on a machine so old, you can forget about watching DVD-Video discs, hell even early G3s have trouble decoding DVDs.

As for DVD-RAM, I'm fairly sure there's a solution to allow 68ks to run DVD-RAM drives, can't remember the name though. Either way, good luck finding a SCSI DVD-ROM or DVD-RAM drive.