XULRunner is a project that has been around since the inception of Firefox, and predates Adobe AIR by quiet a margin. For those who have not really looked into it too much, XULRunner has a lot of similarities to Adobe AIR – it is a cross platform runtime that allows you to run code written in XUL – an XML derivative very similar to HTML.
I haven’t played with XUL a whole lot since AIR came out, as documentation has always fallen behind AIR’s. And performing some advanced functions, like populating a tree component with SQLite results, or manipulating an image, are a little more involved than with AIR.
However, XULRunner has been really branching out to a lot of platform – Windows, Mac OS and Linux support was all there before AIR even came on the scene. There is also SkyOS support, and today the first “pre-alpha” of XULRunner is available for Windows Mobile (codenamed “Fennec”). There are also lightweight ports available for mobile Linux distros, and for Symbian S60.
This really opens a lot of doors for developers – your desktop applications and mobile applications can all share the same codebase. XUL itself is actually quiet nice to write in, and I was always impressed by how it always took advantage of native OS components libraries.
Anyway, I think the XULRunner team deserves very high praise for what they have accomplished – they have always been ahead of the game when with their platform independent runtime, and they are continuing to push support to an impressive array of platforms.