I've posted on this topic before.
From an interview with CTO of Laszlo Systems:
But now that the source code is open and available, we're working on establishing alliances to get this platform, especially the LZX language, to be a standard. That benefits us and the industry because this is the open Web. It's open source. It runs everywhere and runs in any browser.
Competition with Longhorn's XAML platform from Microsoft is mentioned, but Mozilla's XUL is not. What does this mean for the future of XUL? Will the split of competitor's between XUL, Laszlo, and the proprietary Macromedia Flex allow Microsoft to win?
The primary incompatibility between XUL and Laszlo is that XUL requires some portion of the Mozilla runtime environment to run, whereas Laszlo uses Flash. With Flash having a much larger install base, people look at Laszlo as being essentially zero-install on the client.
What I would like to see is Mozilla and Laszlo work together to come to a standard on the XML UI language. Then Laszlo could continue to produce a Flash-based implementation, while Mozilla continued to produce it's current implementation. Both implementations have pros and cons. Flash is cross browser; Mozilla is themeable, and has more native-like widgets.
I don't know what the currently techincal differences are in the languages, so I don't know how far away this concept would be to achieve. But I really think that it's got to be started now, if open-source is to compete in this field with Microsoft. Any ideas on how to get this ball rolling?