ooRexx

Open Object Rexx (ooRexx) is an Open Source project managed by Rexx Language Association (RexxLA) providing a free implementation of Object Rexx, an enhancement of classic Rexx; a powerful, full-featured programming language which has a human-oriented syntax.

The Open Object Rexx interpreter allows you to write programs procedurally as well as in an object-oriented fashion. 

Provides a standard Rexx API to develop external function libraries written in C. Available for Windows, Linux on various instruction set architectures, and MacOSX.

Regina

Regina is an ANSI-compliant Classic Rexx interpreter that has been ported to most Unix platforms (Linux, FreeBSD, Solaris, AIX, HP-UX, etc.) and also to OS/2, eCS, DOS, Win9x/Me/NT/2k/XP, Amiga, AROS, QNX4.x, QNX6.x, BeOS, MacOS X, EPOC32, AtheOS, OpenVMS, SkyOS and OpenEdition. Rexx is a programming language that was designed to be easy to use for inexperienced programmers yet powerful enough for experienced users. It is also a language ideally suited as a macro language for other applications. Regina is currently licensed under the GPL and is maintained by RexxLA officer Mark Hessling.

NetRexx

NetRexx blends the clean, easy-to-learn syntax of Rexx with the robustness and portability of the Java™ environment. The result is a language tuned for both scripting and application development, and designed for both interpretation and compilation – a truly general-purpose language.
NetRexx is an effective alternative to the Java language, letting you create applications and applets for the Java environment faster and more easily than by programming in Java.
Being very system-independent, NetRexx offers the advantages of portability to almost any operating system that supports a Java Virtual Machine (JVM)..

BSF4ooRexx

BSF4ooRexx is a Java language binding for the scripting language ooRexx. BSF4ooRexx allows ooRexx programmers to immediately use all Java classes directly as if they were plain ooRexx classes in an easy and straightforward manner. In addition it adds ooRexx as a macro language to Java, making it easy to employ ooRexx as a script language for Java. BSF4ooRexx even allows one to implement Java interface or abstract methods with ooRexx.