That enough initials for you? The reasoning behind the decision is long and complicated, and no one is completely happy with the situation. If you want all the details, go listen to the BBC's Backstage podcast explaining the situation. What it seems to boil down to is nobody wanting to, or being able to, drain the swamp of ambiguous rights, partials ownerships, and uncertain licensings that surround the BBC's massive content and performance archives.

In an attempt to build an umbrella over the whole mess that would permit some kind of content exposure without massive groundwork, the BBC put out a new "iPlayer" software that requires the person to have Microsoft DRM. They make the argument that they evaluated a number of open standards and found nothing that met their needs. So given a choice between stasis and a limited solution they picked this limited one.

If there's a bright spot in this story, it's that the BBC Trust, which oversees the various Beeb operations, has only permitted this as a temporary solution and "...will require the BBC Executive to adopt a platform-agnostic approach within a reasonable timeframe." Let's hope that open alternatives can meet the eventual challenge.