WebObjects is a an integrated suite of freely available Java frameworks and tools that helps a developer to develop scalable, sophisticated applications for the Internet on most computers with Java support.
It is the most mature platform available for enterprise level web server development, providing object oriented framework support for relational database object persistence (in any JDBC compliant database), Ajax, Web Services, streaming media, Java Client, Rapid Application Development, file upload/download and many other popular web technologies.
Originally developed by and for NeXT computers in the mid 1990's, it was ported by Apple to Mac OS X and Mac OS X Server under Objective C and then completely translated to Java. It is the technology on which Apple's own iTunes Music Store was developed.
It has a very active and helpful developer community with mailing list support at the WO Developer Mailing List.
As of WebObjects 5.3, the deployment of WebObjects-based server applications is now permitted on any platform. The Xcode 3.1 license (The last that included any reference to WebObjects) stated this:
D. WebObjects Software. Subject to the terms and conditions of this License, you may incorporate the WebObjects Software included in the Developer Software into application programs (both client and server) that you develop on an Apple-branded computer. You may also reproduce and distribute the WebObjects Software unmodiﬁed, in binary form only, on any platform but solely as incorporated into such application programs and only for use by end-users under terms that are at least as restrictive of those set forth in this License (including, without limitation, Sections 2, 6 and 7 of this License).For avoidance of doubt, you may not distribute the WebObjects Software on a stand-alone basis, and you may not develop application programs using the WebObjects Software (or any portion thereof) on any non-Apple branded computer.