REALbasic is a cross-platform software development environment for developers who want to create and deliver native applications for Mac OS, Windows, and Linux. For example, you can create an application for Mac OS and Linux from a Windows machine. It is intended for people with all levels of programming experience. It is object-oriented, powerful, and supports advanced programming concepts like inheritance, polymorphism, interfaces, delegates, introspection, etc.
Green Dome GNUstepWeb for Mac OS X provides a WebObjects 4.5-like environment for Mac OS X (with some support for WO5 additions). It is composed of modified versions of the standard GNUstepBaseAdditions, GDL2, and GNUstepWeb frameworks, built to run on top of Apple's Cocoa frameworks. The GNUstep frameworks have been built with Xcode as true Mac OS X frameworks. Thus, they may be used as any other framework under Mac OS X. Note that this is a standalone package that does not require or interoperate with a separate GNUstep installation/environment. It is not intended to provide a complete GNUstep environment, such as would be expected of a full GNUstep installation.