I have never seen a keynote file. If that's some open source format, then there is likely a windows port of the software needed to read it.

However, given that I have used the internet for years and never seen one, it doesn't strike me as important.

Edit: I don’t know why the parent is down-modded. I imagine this is one of the most common criticisms that Scribd will get. Why do I need it? And yes, I watched the intro video.