STklos is a free Scheme System conforming to R5RS. The implementation is based on an ad-hoc Virtual Machine. It can also be compiled as a library, so that one can easily embed it in an application. Its features include an efficient and powerful object system based on CLOS, a simple-to-use module system, implementation of the full tower of numbers defined in R5RS, and easy connection to the GTK+ toolkit. STklos is the successor of STk, a Scheme interpreter tightly connected to the Tk toolkit.
SWI-Prolog is an implementation of the Prolog language which aims to provide a free, user-friendly, fast, and scalable platform for learning Prolog, for doing research in logic programming, and for application development. With its XPCE graphics library, it provides a development environment for Prolog and portable (Unix/X11, Windows, and Mac OS X) graphics to applications. It features a very fast compiler, compliance to ISO and many de-facto standards, scalability, modules, garbage collection (even for atoms), fast two-way C and C++ interfaces, embeddability, last-call optimization, and portability (ANSI-C, 32 and 64-bit platforms).
The Table Driven Assembler (TDASM) is a portable cross assembler for any kind of assembly language. It should be possible to use it as a compiler to any target microprocessor using a table that defines the compilation process. The development of the project has been terminated. Anyone who would like to continue with development is welcomed, but there is only czech documentation available.
The Glasgow Haskell Compiler is a robust, fully-featured, optimising compiler for the functional programming language Haskell. GHC compiles Haskell to either native code or C. It implements numerous experimental language extensions to Haskell for example concurrency, a foreign language interface, several type-system extensions, exceptions, and so on. GHC comes with a generational garbage collector, a space and time profiler, and a comprehensive set of libraries.
Harbour is a free, cross-platform compiler for the Xbase language. It is designed to be as compatible with CA-Clipper as humanly possible. Harbour ships with full source and makefiles, and combined with one of many C compilers will create executables which run natively on the following platforms: Linux, FreeBSD, DOS, Windows 3.x/9x/NT/W2000, and OS/2.
The Kawa Scheme System is a full Scheme implementation, completely written in Java. Scheme functions and files are automatically compiled into Java byte-codes. Kawa does some optimizations, and the compiled code runs at a reasonable speed. It provides the usual read-eval-print loop, as well as batch modes. The Kawa compilation framework is also useful for implementing other languages on top of JVM. There is active development of XQuery (the XML query language), and less active development of Emacs Lisp, Common Lisp, and EcmaScript.
TinyCOBOL is an effort to bring a free COBOL compiler to Linux. It generates GNU assembler for the i386 Linux platform. A executable binary is then created using the GNU assembler and linker. The project is approaching the first beta release with many statements already implemented.