Um, hasn’t Seemsic run on Windows all along? Well, yes, but that’s because it’ s written in Adobe AIR, an application platform that lets programmers write Flash applications that can run outside the browser. (That’s a dumbed-down explanation of AIR, but enough to get the gist across, I hope.) One of the principal selling points of AIR is that it lets developers write one app that runs on Windows, Mac OS X, and Linux, as Seesmic Desktop does.

In theory, the existence of an AIR version of Seesmic should eliminate the need for the company to bother with a Windows one. To date, though, AIR hasn’t been a miracle cure for incompatible operating systems. Some good stuff has been built with the technology–including Seesmic, archrival TweetDeck, and Times Reader–but AIR is notorious for hogging memory and computing cycles. And AIR apps’ user interfaces tend to feel a little foreign, too–there’s still something to be said for Windows apps that feel like Windows apps, and Mac ones that feel Maclike.

The state of AIR feels uncannily similar to the situation with Sun’s Java back in the 1990s. Java was also supposed to let programmers stop worrying about incompatible operating systems. Companies built ambitious products such as entire office suites in Java. But while Java did have a major impact on the world–among many other things, it’s the basis of RIM’s BlackBerry OS–it did little to reduce the need for native applications for Windows, OS X, and Linux. That was in part because it had a reputation for…hogging memory and computing cycles, and for producing apps that felt a little foreign.

Bottom line: Inside the browser, platform-independent technologies have flourished, including open standards such as JavaScript and proprietary ones such as Adobe’s Flash. Outside the browser, not so much. Come to think of it, I like Seesmic’s entirely Web-based app a lot more than the AIR version.

Oddly enough, there’s major AIR news today: Adobe has unveiled a beta of AIR 2, which is supposed to be less piggish and to permit more native-feeling programs. (It may or may not be a coincidence that Adobe announced the new version during Microsoft’s big conference–you be the judge.) I still like the idea of platforms like AIR, and am glad Adobe is continuing to plug away at at it. Unlike some people, I’m not an AIR hater. But come to think of it, I’ve tried a whole bunch of AIR apps over the past year, and usually abandon them pretty darn quickly.

For now, I understand completely why Seesmic decided to go native in Windows. Wonder how long it’ll be until there’s absolutely no reason to write an app for a particular OS?