GNAT (formerly the GNU NYU Ada Translator) is a full Ada compiler and runtime library supporting Ada 2005, Ada 95, and Ada 83. It is a full implementation of the language, including all of the optional Annexes of the Language Reference Manual. It is based on GCC technology, and has source, pre-packaged releases, and several additional Ada tools available. The runtime has a modified GPL so that your applications don't have to be GPLed automatically.
GNU Prolog is a free Prolog compiler with constraint solving over finite domains. GNU Prolog accepts Prolog+constraint programs and produces native binaries (like gcc does from a C source). The obtained executable is then stand-alone. The size of this executable can be quite small since GNU Prolog can avoid to link the code of most unused built-in predicates. The performances of GNU Prolog are very encouraging (comparable to commercial systems).
Sather is an object oriented language designed to be simple, efficient, safe, flexible and non-proprietary. One way of placing it in the "space of languages" is to say that it aims to be as efficient as C, C++, or Fortran, as elegant as and safer than Eiffel, and support higher-order functions and iteration abstraction as well as Common Lisp, CLU or Scheme.
The GRASP Project has created an algorithmic-level graphical representation for software called the Control Structure Diagram (CSD). The CSD was created to improve the comprehension efficiency of Ada source code and, as a result, improve software reliability and reduce software costs. Since its creation, the CSD has been expanded and adapted to include other languages. GRASP provides the capability to generate CSD's from Ada 95, C, C++, Java, and VHDL source code in both a reverse and forward engineering mode with a level of flexibility suitable for professional application. GRASP has been integrated with the GNU family of compilers for Ada (GNAT) and C (gcc), and Sun's javac compiler for Java. Use of GRASP is not restricted to these compilers, however. This has resulted in a comprehensive graphically-based development environment for these languages. The user may view, edit, print, and compile source code as CSDs with no discernible addition to storage or computational overhead.
Gwydion Dylan is a portable, optimizing Dylan compiler written in Dylan. It was originally written by the Gwydion Group at CMU and is now maintained by volunteers. Eventually, Gwydion Dylan is meant to become a top-notch tool for building complicated applications. Dylan is a dynamic, object-oriented language with four design goals: high performance, rapid prototyping, ease of use, and seamless support for using libraries written in C. Ports of Gwydion Dylan are available for many platforms.