Dave Winer : If I had one wish, it would be that everyone who reads this blog would listen to the talk I gave to the NPR people last Thursday

Dave Winer on his ideal podcast player

3. Must be a platform, that is, people other than the manufacturer can add apps.

An intriguingly succinct definition of "platform". You can see how it works. A platform must be something that multiple agents (manufacturers) have to collaborate (and sometimes compete) around. If not, there is no real platform war possible. Platform Wars are competitions for the hearts and minds of developers.