The obvious solution for interoperability is to choose some form of MPEG-4 without any DRM. I could play an MPEG-4 video on my MacBook Pro, my FreeBSD machine, my Symbian phone, my Nokia 770, and the iPod I don't own. Looking back at the BBC charter, I find my eye drawn to this section:
Does DRM deliver the benefit of emerging communications technologies? Internet-connected desktop PCs are certainly not emerging; they are old and boring technology that is on the decline. By locking content to a single supplier's products, they reduce innovation. Any product that is built to take advantage of the content made available by the BBC though the iPlayer must run Windows, or must contain technology licensed from Microsoft. Unlike the BBC, Microsoft are a for-profit corporation who have no requirement to license their technology for use in products that would threaten their business.
In an era when even EMI are selling their content without DRM, it seems somewhat anachronistic to be considering introducing a new product based on it.