Prism, meet your brother, Fluid
Prism is a technology from Mozilla Labs based on the earlier work on Webrunner. It allows websites, such as Gmail, to be run as their own applications, running outside of a normal Firefox window. This is useful as a basic platform for web developers who want to develop applications based on web technologies but do not want to simply run them as web pages in Firefox. (And, yes, I’m simplifying things here a bit but you can read up about it on the Mozilla Labs page or Alex Faaborg’s blog post on Prism as well.)
Today, there was a post on the Compiler blog about a similar technology called “Fluid.” Fluid is similar in conception to Prism but is based on WebKit, rather than Gecko. The site for it (coining the term, I believe, of “Site Specific Browsers” or “SSB”) states that it is inspired by Prism but relies on different strengths, namely of being a native feeling application on a Mac:
What makes Fluid different from Prism? Prism is cross-platform and based on the Mozilla web rendering engine, Gecko. While Prism's cross-platform nature means it can be run on Windows, Mac, or Linux, it also means SSBs created by Prism aren't the most "native"-feeling applications on Mac OS X. Thus Prism forfeits one of the major benefits of Site Specific Browsers: making a webapp feel more like a native desktop app. Fluid is very similar in nature to Prism, but is based on Safari's WebKit rendering engine. And SSBs created by Fluid are true, native Cocoa OS X applications offering seamless integration into the Mac OS.
I applaud the development of more applications and frameworks like this but I’m not really sure that we need it. For those that prefer WebKit, this makes an interesting addition and we’ll see how far Todd Ditchendorf, the developer, runs with it. Personally, I think that one of the great strengths of Prism, as it develops, is that is is cross-platform. I think that is an advantage that far outweighs any look and feel benefits that Fluid may offer. I also prefer the direction that Gecko is going in, overall, as a platform, and the community around it, over that of WebKit but obviously I am biased here.
You can download the beta but I did notice it is Leopard only so Tiger users are out of luck.
Todd has put together a Youtube video highlighting the work on Fluid.