Firefox for Windows 8's "Modern" user interface (UI) will likely wrap up development in November, Mozilla said on its website in a best case-worst case schedule.
A new addition to a Mozilla wiki noted that the browser will be completed Oct. 2, 2013, at the earliest, or nearly a year after the launch of Windows 8. But the project could be delayed until March 20, 2014. The most probable finish date -- based on programming pace so far -- is closer to the former than the latter: Nov. 19, 2013.
According to Mozilla, it's a third of the way through development of Firefox for the Modern UI.
Mozilla started work on a Modern edition of Firefox, one that would run in the UI formerly known as "Metro" on Windows 8, more than a year ago. The open-source developer released a Windows 8 Firefox preview last October.
At that time, Mozilla's schedule claimed that the Firefox app might appear as early as January 2013 in a dual-browser package along with the company's better-know desktop browser.
The long development cycle speaks not only to the complexity of building a browser from the ground up, but also hints at the difficulty programmers have had writing high-quality Modern apps.
Michael Cherry, an analyst with Kirkland, Wash.-based Directions on Microsoft, who has built Modern apps for his own business use, has expressed frustration with development difficulty, especially for programmers like himself, who come from years of experience crafting code for the Win32 APIs.
Cherry's knocked Microsoft's documentation for WinRT -- the API (application programming interface) core to Windows RT -- and wondered whether all programmers have had the same trouble switching from old, familiar tools to those required to build Modern apps.
"I don't remember a disconnect like this before," Cherry said in a recent interview, referring to developer expectations versus results.
Third-party browser makers also face unique hurdles in Windows 8.
Only the default browser -- which is set by the user -- can run in the Modern UI; during setup, Windows 8 assigns Internet Explorer 10 (IE10) as the default browser. Even so, Mozilla has said it's important that it have a Modern browser app to remain competitive as Windows 8 gains traction.
Windows RT, the touch-only spin-off designed for tablets, is a different story, however. Unlike Windows 8, Windows RT bars all third-party developers from accessing the limited "desktop" mode; only Microsoft's programmers can call the APIs there, which they do to power much of the Modern version of IE10 on the tablet OS.
A year ago Mozilla accused Microsoft of anticompetitive behavior by purposefully blocking others from building browsers that could effectively compete with IE10 on Windows RT.
Google has a Modern version of its Chrome browser as well, which can be downloaded from its website. Like Firefox, Chrome on Modern works only on Windows 8, not Windows RT.
Users can download Firefox for Windows 8, by following the instructions under "Nightly Builds" in the "Metro Builds" section of this Mozilla wiki page.
This article, Best case, Mozilla's Firefox for Windows 8 will ship in October, was originally published at Computerworld.com.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.