Hi Lee - unfortunately, video playback is a complete rats' nest even just on Windows, as I know to my cost over the last 13 years working on our Language Lab software. New standards come out all the time, and different platforms like or dislike them.
On Windows you really need to use the DirectShow subsystem for playback, and each video standard needs a user-install of the appropriate (or often not appropriate!) filters. The only video standards guaranteed to work on Windows are MPEG-1 and WMV.
On Android currently: H263 H264 MP-4. WebM(VP8) is available on Android 4.0 and up.
On iOS: .mov, .mp4, .m4v, and .3gp
Mac OS - various with installed codecs.
HTML5 standards group originally wanted to make Ogg video and audio a requirement for browsers, but as usual, Apple objected. As a result the HTML video and audio tags provide for multiple versions of a video and audio file, and the browser selects the format which it knows about. For a comparison see:
http://en.wikipedia.org/wiki/HTML5_video
Then there's the problem of rendering the video in OpenGL. There's a discussion of it here:
http://lurkertech.com/lg/ogl.video.html
So it looks as though whatever implementation is used, programmers will have to provide content in at least two formats, and probably in different sizes. On OpenGL it may be necessary to ensure that the video dimensions are ^2
For intro video or cut scenes it may be simplest to call out to the platform's default browser or media player and let that do the work. It's not elegant, but it's fast to implement.
Sorry for the long post, but I think it's important for people to understand that implementing video playback is a very complex issue indeed. There is no simple "out of the box" solution, and that's why AppGameKit (and Monkey) have so far not supported it.
-- Jim