XUL Runner is currently a product in development which provides a runtime environment for XUL applications. Therefore all XUL applications for Mozilla FireFox, Mozilla Thunderbird, Democracy Player and Songbird willbe able to executed using this product. Currently XulRunner 1.8.0.4 is the most stable build so far with XUL Runner 1.9 (the first production version) scheduled to be released with Firefox 3 late into 2007.