AppleComputer's (formerly NeXT's) WebObjects frameworks, are basically, a set of frameworks building on the FoundationKit, for making web applications. An example of this is AppleComputer's own Apple Store, which is run by means of a WebObjects application (or was last I saw).
WebObjects 5 was just released, and the deployment platform is Java and therefore should work on any JRE1.3 platform! Yay! However, I quote: (1) WebObjects 5 is officially qualified for use only on Mac OS X, Windows 2000 Pro, and Solaris 8 using Oracle 8i with JDBC 2 and the Java 2 Platform, Standard Edition 1.3. Although I guess linux might work :)
Unfortunately, WO is pay-for software. Currently, the price is $699 (originally, it was $50,000 for an unlimited-user license!!!).
Paying ADC members get a free development license.
See http://www.apple.com/webobjects/ for more information.
The SOPE application server which is part of OpenGroupware.org includes an almost complete implementation of the WebObjects 4.5.1 framework under the LGPL license, that is, an Objective-C implementation of WO.
See http://www.opengroupware.org/en/devs/sope/ for more information. Looks like it needs a LOT more info on the site, etc. to make people feel comfy. ;-)
GNUstepWeb is written in Objective-C and designed to be source-code compatible with WebObjects 4.5.
WebObjects is now free for everyone to use and is included with the Xcode 2.1 Developer Tools.
Sure that applies to deployment as well?
WebObjects deployment is free with OS X Server, but the XCode Tools don't include a deployment licence.