Presentation: Why Free-Libre / Open Source Software (FLOSS or OSS/FS)? Look at the Numbers!

This is the home page for the presentation “Why Free-Libre / Open Source Software (FLOSS or OSS/FS)? Look at the Numbers!”. This presentation is a summary of my paper, titled “Why Open Source Software / Free Software (OSS/FS or FLOSS)? Look at the Numbers!”, and its supporting database on OSS/FS quantitative data. Both the paper and presentation provide quantitative data to show that, in many cases, free-libre / open source software (FLOSS) is equal to or superior to their proprietary competition. The goal is not to show they are always superior... just enough to show you that you should consider them when acquiring software. Both the paper (with supporting database) and the presentation examine market share, reliability, performance, scalability, scaleability, security, and total cost of ownership; they also both comment on non-quantitative issues and unnecessary fears.

If you want the long, detailed, and complete version, see the supporting database or paper. You may also be interested in the discussion group for quantitative numbers about free / libre / open source software. If you want the short version, in presentation form, you're at the right place!

Getting the Presentation

Just choose the language and format you'd prefer. For just reading, choose PDF; if you want to modify it (say to include in your own presentation), choose OpenDocument (and see the license information below):

Language PDF OpenDocument (.odp) Date
English PDF (English) OpenDocument (.odp) (English) 2011-04-17

PDF is Portable Document Format, a read-only format that can be viewed with Adobe Acrobat, xpdf, evince, and many other viewers. (Note: evince 0.4.0 has a known printing bug; use an alternative if you print.) The PDF has the presentation twice: first, it has the just the presentation slides (full page); this is followed by the annotated slides.

OpenDocument format is the only international standard format for exchanging editable office documents. Wikipedia's article on OpenDocument explains OpenDocument further, if you're not familiar with it yet. OpenDocument's .odp format is for presentations, and thus it's like the obsolete .ppt Powerpoint format. However, OpenDocument is based on XML (with XML's many advantages) and is an open, public standard that anyone can implement. If you don't have a program that can read OpenDocument files yet, one simple solution is to install the freely-available office suite. There are other FLOSS and proprietary programs that read the OpenDocument format, including KOffice, StarOffice, and others (see the Wikipedia article for more). OpenDocument isn't specific to OSS/FS, but since there are OSS/FS programs that support it and it's the only international standard for this purpose, it seemed very appropriate to use it.

More about the Presentation

This presentation is a summary, giving you a quick summary of some of the most interesting or relevant studies. In contrast, see the paper “Why OSS/FS? Look at the Numbers!” if you want to see complete set of studies or more information about the studies. That paper is the most complete collection of such statistics in the world, to my knowledge, and I try to keep it complete. But because it’s grown so large, many people would rather have the “short form” of the work.

This briefing was given in 2005 in Porto Alegre, Brazil, at the 6th International Free Software Conference (FISL 6.0). I’ve given various versions of it many other times over the years.


This presentation uses Microsoft’s True Type core fonts. As noted in this font HOWTO, this should make it easier on Microsoft Windows users, who often don’t know how to install fonts on their systems. These fonts are also available to Linux users (Microsoft's license allows this), so it allows universal access. If you don’t already have these fonts, you can get Microsoft’s True Type core fonts for Linux here. RPM-based systems such as Fedora Core can get Microsoft’s True Type core fonts for Linux prepackaged in RPM format for Fedora Core.

I experimented with the high-quality Bitstream Vera fonts, which are available to all users of and have a simpler license, but not everyone has them.

Can you Link Here?

Yes, please link to this page, but please also include a link to, the address of the more detailed study on OSS/FS this is based on. I want to make sure that people can find the original work, and including links to it from the remote sites directly to it will make that possible.


Can you redistribute the originals, or edit these presentations for your own use? Yes, you can.

The presentation is (C) Copyright 2005 David A. Wheeler. You may distribute unmodified and modified derivative copies of the document in electronic form, print form, or any other medium, under certain conditions; in particular, this work is “copylefted”. More specifically, you can release unmodified or modified versions under any one or more of the following copylefting licenses (unless you specifically say otherwise, you’ve released any derivative work under all of these licenses):

  1. Creative Commons Attribution-ShareAlike 2.5 License. Under this license, you are free to (1) copy, distribute, display, and perform the work; (2) make derivative works; and (3) to make commercial use of the work. However, this freedom is under the following conditions:
  2. GNU General Public License (GPL)] version 2 or greater.
  3. GNU Free Documentation License (GFDL) version 1.2, November 2002 or later.

Although it’s not a license condition, please include a reference to this page ( and also the original work ( in any derivative, so that others can find this material. By releasing this material under multiple licenses, I intend increase the odds that it will be compatible with others’ documentation.

Note that I have not released the original paper with the same conditions; see that paper for its conditions.

Suggestions for Editors

If you want to edit these files, you simply need to get a program that can edit OpenDocument files.

If you choose to use 2, you can generate the PDF the same way I do. Simply choose "File/Export as PDF", check the filename and then select "Save". Then select Range: All pages, Images: Lossless, and General: Tagged PDF, Export Notes, Use Transition Effects. I do not suggest turning on "Tagged PDF"; it has some nice extras, but the file balloons to 3.5M in size, as opposed to 475K, so it's probably not worth it. Select "Okay". This generates the file as (1) the slides, then (2) the annotated slides. A single PDF with both versions makes my life much easier -- I only have to track one PDF per edition, and people can then print the range of pages they want.

Tracking Changes

If you need an old version of this presentation, go look at the archive for this presentation. If you want to see what has changed in this presentation or the paper (I keep a single ChangeLog that discusses both), see the Look at the Numbers ChangeLog.


Please contact me if you’re interested in translating it, I’d like as many translations to become available as possible.

There are several translations of my massive tome of statistics, for which I'm grateful, but many translators have told me that it's just too long for them to translate. In contrast, this presentation is quite small, and even the annotations are not that much. So I'm hoping that there will be many people who will translate this document.
About the Author

David A. Wheeler is an expert in computer security and has a long history of working with large and high-risk software systems. His books include Software Inspection: An Industry Best Practice (published by IEEE CS Press), Ada 95: The Lovelace Tutorial (published by Springer-Verlag), and the Secure Programming for Linux and Unix HOWTO (on how to create secure software). Articles he’s written related to OSS/FS include More than a Gigabuck: Estimating GNU/Linux’s Size, How to Evaluate Open Source Software / Free Software (OSS/FS) Programs, Comments on Open Source Software / Free Software (OSS/FS) Software Configuration Management (SCM) systems, Make Your Open Source Software GPL-Compatible. Or Else, and OSS/FS References. Other security-related articles he’s written include Securing Microsoft Windows (for Home and Small Business Users), Software Configuration Management (SCM) Security, and Countering Spam Using Email Passwords. Other articles he’s written include The Most Important Software Innovations, Stop Spam!, and an article on Fischer Random Chess (Chess960). He has released software as well, including flawfinder (a source code scanner for developing secure software by detecting vulnerabilities) and SLOCCount (a program to measure source lines of code, aka SLOC). Mr. Wheeler’s web site is at You may contact him using the information at but you may not send him spam (he reserves the right to charge fees to those who send him spam).
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