When version 3.0 of the Flickr Uploadr came out, we Flickr users got a significantly more useful tool for getting photos online. But things changed significantly behind the scenes as well.
XULRunner is a Mozilla runtime package that can be used to bootstrap XUL+XPCOM applications that are as rich as Firefox and Thunderbird. It will provide mechanisms for installing, upgrading, and uninstalling these applications. XULRunner will also provide libxul, a solution which allows the embedding of Mozilla technologies in other projects and products.
The choice to build on XULRunner is something that I discussed with Richard Crowley. Building on top of a Mozilla engine isn't new, of course. ActiveState has been doing so for years now for their Komodo IDE, as ActiveState founder Dick Hardt and I discussed in this interview at the 2007 Defrag Conference. The difference is that the platform is far more mature and feature complete now.
Unlike previous versions of the Uploadr, version 3.0 is available under an Open Source license (the GPL version 2). You can get the source code here if you'd like to poke around and add a feature of your own.
It's a pattern that seems to repeat itself time and time again: Open Source infrastructure maturing and eventually replacing proprietary systems.
Yahoo! Developer Network