What? Unless the entirety of your information about the AppleTV comes from Cory Doctorow posts, you know that the only places DRM comes into the picture are when streaming pre-existing content from premium sources (iTunes Store, Netflix, Hulu).
There's absolutely nothing stopping you from loading a DRM-free h.264 file on another one of your Apple devices and streaming that over AirPlay. And HTML5 video in Mobile Safari works beautifully.
Not (entirely) true at all! Someone reverse-engineered most of the Airplay protocol, so you could (if you wrote software to do it) do the same stuff on Windows/Linux/Etc: http://nto.github.io/AirPlay.html
For video streaming, you basically just have to send it a URL to a video file, and it'll stream and play it for you just fine.
The DRM on Netflix is so strange. On my parents' AppleTV and some Toshiba TV, they often get HDCP errors when viewing Netflix. Now, Netflix works on plenty of other devices without HDCP. So the addition of DRM there achieves absolutely nothing other than to delay or cause errors for legitimate users.
There's absolutely nothing stopping you from loading a DRM-free h.264 file on another one of your Apple devices and streaming that over AirPlay. And HTML5 video in Mobile Safari works beautifully.