DRM -- Digital Rights Management, or Digital Restrictions Management -- is technology that prevents you from using some files by taking over part of your computer so that it won't obey your requests. DRM is always proprietary. Before a DRM is released, it is infected with "Hook IP" -- a patent or trade secret that is introduced to the technology so that the only way you can implement the DRM is by licensing the Hook IP. Anyone who licenses the Hook IP is forced to promise to make their DRM behave as intended, preventing uses and taking over computers and devices. Without Hook IP, a company could implement the DRM but leave out the restrictions, shipping products that allow all the uses their competitors' products deny. Hook IP gives the DRM maker something to sue over if this happens.
So DRM is by definition proprietary. If it's not proprietary, it can't be DRM.
And, of course, Ogg Theora is not proprietary. It does have some patents covering it, but those patents have been surrendered, to all intents and purposes.
Most importantly, the W3C is probably the purest anti-proprietary standards body on the planet, having already rejected any kind of licensing conditions or fees for its standards, setting the bar for anyone who wants to add to the Web: such additions have to be as free as the Web itself.
Nokia intervention here is nothing short of bizarre. Ogg is not proprietary, DRM is, and DRM-free may be a "non-starter" for Hollywood today, but that was true of music two years ago and today, most of the labels are lining up to release their catalogs without DRM. The Web, and Web-based video, are bigger than Hollywood. The Web is not a place for proprietary technology or systems that take over your computer. For Nokia (and Apple, who also lobbied hard for DRM inclusion) to get the Web this badly wrong, this many years into the game, is really sad: if you haven't figured out that the Web is open by 2007, you just haven't been paying attention.
Some Slashdot commenters have pointed out that they have technical problems with Ogg Theora. That's a valid discussion to have -- if the W3C is going to pick a video codec, its technical merits should be discussed. But remember, that's not what Nokia is objecting to: they are arguing that Ogg is proprietary (it isn't) and that DRM should be part of a Web standard (it shouldn't). PDF link to Nokia's W3C submission, Link to Slashdot comments