Free and Open Source Software
Objective-C
A general purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Objective-C was specifically designed for the Apple ecosystem and their respective application programming interfaces, Cocoa and Cocoa Touch for building applications for macOS and iOS. Since 2014 the Apple ecosystem rely on their new programming language Swift.
Lisp
A family of programming languages dating back to 1958. Lisp is the second-oldest high-level programming language in widespread use today.
Rebol
Rebol is a lightweight, cross-platform data exchange programming language. The language is designed by Carl Sassenrath and is suited for network communications and distributed computing. Rebol's unique simplistic design makes it a productive language that is loved by its users.
Racket
Racket started its life as a Scheme implementation, but has now grown into a general-purpose, multi-paradigm programming language and the world's first ecosystem for language-oriented programming. Racket designed to be a platform for programming language design and implementation where developers can create their own dream language.
ReactOS
ReactOS is a free and open-source Windows-like operating system for amd64/i686 computers. ReactOS was designed to be binary-compatible with computer programs and device drivers made for Windows Server 2003 and Microsoft Windows NT family of operating systems including Windows NT4, Windows 2000, Windows XP, Windows 2003, Windows Vista and Windows Seven. To Some, ReactOS is a potential open-source drop-in replacement for Windows and for its information on undocumented Windows APIs
Midori
Midori is a free and open-source web browser based on GTK and Webkit. The browser is lightweight and fast that works cross-platform.
Eiffel
Eiffel is an free and open-source object-oriented programming language designed at Eiffel Software by Bertrand Meyer back in 1985. Bertrand Meyer had one goal in mind when he created the language, the goal of increasing the reliability of commercial software development. Today Eiffel comes with its own IDE (Integrated Development Environment) called EiffelStudio, the software can be used to write Eiffel code in a single user interface that includes a compiler, interpreter, debugger, browser, metrics tool, profiler, diagram and code inspector.
Pascal
Pascal is a free and open-source imperative and procedural programming language. The language was designed 1970 by Niklaus Wirth to encourage good programming practices using structured programming and data structuring.
Ceylon
With Ceylon developers can write software that runs on the JVM (Java Virtual Machine) or complied to JavaScript. Ceylon is an object-oriented, strongly statically typed programming language with an emphasis on immutability. The language was first created by Red Hat in 2011, but is now maintained by the Eclipse Foundation.