Two weeks after Steve Jobs signaled that Apple (AAPL) would not be building Flash support into the iPhone, Microsoft (MSFT) on Monday took the opposite stance — signing a licensing agreement with Adobe (ADBE) for both Flash Lite and Reader LE in its competing Windows Mobile platform. (link)

This despite the fact that Microsoft is working on a product — Silverlight for Mobile — that is expected to compete directly with Flash Lite.

What’s going on here?

First a bit of background. Flash (short for FutureSplash, one of its early incarnations) is a set of multimedia technologies widely used by advertisers, game companies and Web developers to integrate video and other rich media into Web pages. Flash Lite is a subset of Flash used to deliver multimedia content on many Internet-ready cellphones, but not the iPhone.

Asked at the March 4 shareholders meeting when Apple planned to bring Flash to its mobile Web browsers, Jobs said that the PC version of Flash “performs too slow to be useful,” and that Flash Lite “is not capable of being used with the Web.” (see here and here and here)

That’s not quite right. Adobe points out that there are more than 500 million Flash-equipped mobile handsets shipped worldwide, a number that it expects to grow to 1 billion by 2010. (link)

But not if Jobs can help it.

What does he really have against Flash? According to Daniel Eran Dilger at Roughly Drafted Magazine, it has less to do with performance and everything to do with proprietary standards.

Flash video is encoded using a proprietary codec licensed from On2 and served on the web via a Flash-based controller. … By pushing alternatives to Flash, Apple gets a shot at knocking out the headlights of Verizon and all of the hardware rivals lined up behind Adobe’s Flash Lite, including LG, NTT DoCoMo and Sony Ericsson, all of whom hope to use Flash Lite to provide their Symbian phones with a consistent graphical interface.

Were Flash Lite to gain momentum, it might make Adobe the Microsoft of mobiles, and Flash Lite the new Windows. That also makes it obvious why Apple wants to choke Flash to death before it falls into position as the new lowest common denominator in proprietary platforms on a new crop of mobile devices.

Adobe likes the idea of establishing Flash Lite as a banal yet good enough layer of uninspired user interface technology to act as a glue to bond together the fractured Symbian platform. Cutting a deal to stir Flash Lite into the toxic BREW of Verizon also made for a good press release suggesting wide adoption of Flash Lite.

Add in Adobe’s AIR/Apollo system for developing “rich Internet applications” that depend upon Flash, and you have the makings of a Windows-wannabe strategy, giddy to send the increasingly open, cross platform web back into a proprietary prison with Adobe, not Microsoft, holding the key.

Microsoft, of course, would much prefer that it and not Adobe hold that key. But if it comes down to a question of open technologies versus proprietary, guess where Redmond will take its stand?

Apple, of course, is no stranger to proprietary platforms. It just prefers them to be its own.