I think the assumption is that Google still has less than 1 million servers (Google it, most people think they have 1/2 million right now), so this is architecting for more than they need.
It doesn't use WebDAV, it uses Exchange Web Services, which is a standard API for developers to build their own Exchange clients.
I know this because it works with the Exchange 2010 RC, and Exchange 2010 no longer includes WebDAV.
In fact, the Apple web site states (correctly) that it requires Exchange 2007, because Exchange 2003 didn't have EWS.
There is no single "Exchange Protocol." What you might be talking about is MAPI, the protocol Outlook uses to talk to Exchange (and the oldest protocol Exchange supports, I believe). MAPI is full documented on MSDN, and there are a number of open source implementations of MAPI (see http://en.wikipedia.org/wiki/MAPI).
However, the Exchange support in Snow Leopard doesn't use MAPI, it uses Exchange Web Services, which is also open and documented on MSDN.
The article says:
"Apple built its support for Exchange using WebDAV..."
Untrue. The Exchange support for Snow Leopard was built using Exchange Web Services, just like the next version of Microsoft's client, Entourage.
Microsoft is soon to have free-for-consumers anti-virus and anti-malware software as well:
http://www.microsoft.com/security_essentials/
Obligatory Simpsons Reference:
Yay!
But now how will people figure out how to play Video Professor or install AOL?
Oh well...
Perhaps IMAP was not enabled in that Exchange setup...it definitely works, though.
However, to answer your original problem (Firefox and HTML mail), Exchange 2010 does support Firefox (and Safari) using all the features of OWA that IE does, including HTML mail compose.
Exchange works great with IMAP, even if it doesn't exactly follow the delete/expunge model of deletion (but then again, neither does Gmail).
I've used Thunderbird with Exchange 2007 with no problems.
http://www.microsoft.com/protocols/
Actually, it does fall under that category.
Real Programmers don't eat quiche. They eat Twinkies and Szechwan food.
