Python is only one of many important open-source programs that are more than 20-years old.

Today, open-source software is everywhere but many peple still think of it as being relatively new. It's not. Open-source software actually goes back decades.

Before beginning our journey in the way-back machine though we should go over our terminology. "Open source," the phrase, only goes back to February 3, 1998. The phrase was deliberately chosen to separate the more pragmatic open-source supporters from the more idealistic "free software" community members. Gallons of ink and gigabytes of pixels has been spilled on debating the differences between these two, but for my purposes I'm talking about programs that qualify by either definition.

Both concepts were actually used long before proprietary software showed up. As Richard M. Stallman, (rms) free software's founder noted, "When I started working at the MIT Artificial Intelligence Lab in 1971, I became part of a software-sharing community that had existed for many years. Sharing of software was not limited to our particular community; it is as old as computers, just as sharing of recipes is as old as cooking."

For my list, I also decided to skip numerous small programs, such as those in the NASA COSMIC software collection. Some of these date back to the 1960s. Instead, I've focused on major programs, which are still being used today. I also owe a debt of gratitude to Black Duck Software's story, "Oldies but Goodies: Seven Projects still working Open Source."

So, with no further adieu, from the most recent to the oldest, here's my list of older significant open-source projects.

1) Linux: August 25, 1991

There were thousands of open-source programs before Linus Torvalds wrote "I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones." to the Minix Usenet group and unknowingly started the operating system juggernaut that became Linux. That said, Linux has also become the most successful of open-source programs.

Gallery: The 20 most significant events in Linux's 20-year history

Linux has become the foundation for the Internet; the operating system for super-computers; and, thanks to Android, it's becoming the most popular end-user operating system of all. There were indeed other free software programs being released in 1991 and earlier, but none would be more important.

2) Python: February 20, 1991

Guido van Rossum, Python's creator, began work on this important language in December 1989. It wasn't until February 1991, that it was released. Since then, according to Black Duck Software's Ohloh programming statistics, "Python is the fastest growing language in the open source world as measured by number of contributors."

It's not just open-source developers that support Python. Even Microsoft provides a Python IDE (integrated development environment ) for Visual Studio.

3) GNU C Library (glibc): February 1988

That said, C remains a vital language in open-source circles and to do much with C you need a good, general purpose library. Over the decades the most important of these libraries has been glibc. Most of the credit for glibc's early success goes to Roland McGrath. By early 1988, McGrath had given what would become glibc, "a nearly complete set of ANSI C library functions." From this work would spring innumerable programs including Linux.

4) Perl: December 18, 1987

Is there any system or network administrator anywhere who hasn't written at least one script in Perl? I doubt it. Larry Wall's creation has become the go-to scripting language for all servers everywhere. Not bad for a language that was "kind of designed to make awk and sed semi-obsolete."

5) GNU C compiler (gcc): March 22, 1987

If glibc is important then gcc is vital. At its start, gcc only supported C. Today, it supports, to name but a few, C, C++, Objective C, Fortran, and Java. Almost every free software software project owes a debt of gratitude, and a lot of its foundation programming, to gcc.

6) GNU Emacs: 1984

Before there was gcc, the first major GNU program was the GNU Emacs programming editor. While I was never crazy about it—I'm a vi guy—I couldn't begin to count how many programs were written in GNU Emacs. Indeed some people assume that GNU Emacs was the first version of the editor. That isn't so. Emacs actually dates all the way back to 1972.

You could argue that these early versions were also free software, and I wouldn't fight with you about it. There's no question that such early versions as Multic Emacs and Gosling Emacs shared both ideas and code. GNU Emacs, though, became the version that would change the development world.

7) X Window System: 1983

At the same time that Emacs and gcc were starting to roll, others at MIT were working on the X Window System, a TCP/IP-based networking windowing system. No one knew it at the time but X Window would eventually become the basis for all important Linux and Unix interfaces, and the foundation for the Mac OS X interface.

8) BRL-CAD: Dec 16, 1983

If you're a developer, you've heard of all these programs so far, but I'm sure few of you have heard of Ballistic Research Laboratory-computer-aided design (BRL-CAD). This program, which is still being worked on today, is used by the U.S. military to model ballistic attacks on vehicles.

9) First Berkeley Software Distribution (1BSD) Unix: March 9, 1978

The first open-source operating system wasn't Linux. That honor goes to, as Peter H. Salus wrote in A Quarter Century of UNIX, Bill Joy's first version of BSD Unix. When Unix first showed up in 1969, it was open source. Later it was closed, but BSD, the first fork, kept the free software flag flying. While BSD Unix never grabbed the headlines that Linux has, it's actually very important as well. Besides the BSD "distributions," such as FreeBSD, OpenBSD, and NetBSD, both Solaris and Mac OS X got their start from BSD Unix.

10) VistA: 1975

Finally, the oldest open-source program that I know of which is still commonly used is another one you probably haven't heard of: VistA (Veterans Health Information System and Technology Architecture). VistA was the first electronics health record (EHR) system. Today, versions of VistA, such as WorldVistA, Medsphere's OpenVista, and DSS are being used to bring EHR to doctors and hospitals throughout the U.S.

So, as you can see, open-source programs not only has a long history, it's also important in far more places than in software development. Since it's very start, free software has helped us in ways we didn't even know about.

So, the next time, someone says open-source software isn't good or trustworthy, just remind them that not only is it great, it has a better and longer track record than almost any proprietary software.