NCC Members have free access to this Guideline on the Principia website.

Simply defined, Open Source software is software whose original source code is publicly available and may be freely modified or enhanced. It is not, as many people think, defined by its price (or, rather, lack thereof). The ultimate founder of the Open Source movement, Richard Stallman, frequently says, 'Think free speech, not free beer'. His point: to explain what is truly significant about open source (which he usually refers to as 'free software').

Software that is distributed free of charge may still not be Open Source, since the developer may choose not to distribute the software source code or allow its modification. Shareware may be distributed free, either in its entirety or in a demonstration version that is crippled or changed in some way, but it's typically proprietary software whose source code is not distributed. The source code of commercial software is guarded jealously by the company that produces it, and modifications and reverse-engineering are not allowed.

Microsoft has made some effort recently to partially open up the Windows code to selected partners - a process it's dubbed 'shared source', crediting the idea to the open source movement - but with very few exceptions its software remains under control, and remains closed to the general community of non-Microsoft programmers. Those exceptions are the Windows installer, some Windows template libraries, and things like the Office 2003 XML schema, which Microsoft has posted to the main clearinghouse for Open Source projects, Sourceforge (www.sourceforge.net)