ALE is, at its heart, a simple standard whereby components (like the spreadsheet) register callbacks to let the main application know how to marshal (serialize) their data, get an edit interface, get an HTML read-only display, etc. Simple is good, though the cool toys from the Windows world will come with the same costs: DLL hell (imagine if my spreadsheet component uses a different version of a date library than the version my main app uses), speciation over versions of the spec (will ALE 1.0 components work with ALE 2.0 components?), and fragility (as apps are only as stable as their crappest component).
To play with their demo, go to the Zimbra hosted demo and click on the spiral-bound notebook icon on the left. Create a new page, and use the “Insert” toolbar item to add a spreadsheet. I’m still working with Ross to make that easier to get to (and to see whether my Firefox issues are because I’m too bleeding edge, insufficiently bleeding edge, or just that there’s a bug somewhere).
Google Maps was the original mainstream HTML component (as I said in June ’05). Coincidentally, Google just released Version 2 of the Maps API and it includes a (developed in parallel to ALE) system for developers to build and integrate their own controls onto the map. The time must be right to tackle the problems around web components.