Sadly Apple stopped the development of that web solutions years ago and kept it for itself... I heard from various folks at Apple that there are still a few engineers improving it and it is being used a lot for iTunes. WebObjects got some bad reputation from many people that have no clue on how it works and citing that WebObjects can't even support database update and this why the Apple Online Store is often offline when Apple release a new product. This is total BS of course, since take the iTunes AppStore which serve the content for all stores: music, apps, books, movies, etc... And you barely see that iTunes Store is offline.
WebObjects was a great technology but Apple decided to keep it for itself.
Lots, lots more at http://www.wocommunity.org/page/default but as others have said -- this is essentially a (very nice) Java framework with some Eclipse tool support.
What I really miss is the Objective-C framework, with EOF, and native Mac tools, bindings etc.
I think we need a totally new Objective-C framework for web development based on newer design patterns, GCD, etc, but it needs a new port of Foundation and Cocoa to Linux and other systems.
As much as I'd love an Objective-C web framework, I wouldn't use one that only ran on Mac OS, pretty useless in terms of production hosting I think.
Apple moved away from different binaries per platform by switching everything to Java which solve the portability question, and additionally solved the database connectivity issues since by bring a java solution any JDBC driver available to talk to a DB will work with WebObjects.
Overall the move to java was a good move, but Apple stopped the investment in the software that NeXT created and went back to focus on desktop and devices... But they kept WebObjects internally for their own benefits I think.
[1]: https://webkeks.org/objfw/
[2]: https://github.com/Midar/objfw (Mirror)
Midar doesn't slack around when it comes to portability. :)
frothkit looks wrong, reminds me a bit of asp.net.