Open Source, Free Software, and Shared Source. Oh MY!Free SoftwareFree means many different things to different people. Free is such a simple term that you may not think it needs any clarification. We use this term rather loosely; for example, a free world, free enterprise, and of course a free lunch. Well, all I can say is that you better be very sure what is meant when someone refers to "free" software. To clarify matters, the Free Software Foundation (http://www.gnu.org/philosophy/free-swl) has defined "Free Software":"Free software is a matter of the users' freedom to run, copy, distribute, study, change, and improve the software. More precisely, it refers to four kinds of freedom, for the users of the software:
In this context, free then refers to "not suppressing the use of" rather than "reducing the price of" something. Figure 1-1 shows the relationship between Open Source and Free Software. Note that these terms are not interchangeable but are overlapping somewhat. Figure 1-1. Software Licensing Models.[View full size image]  Shared SourceShared Source is somewhat close to freedom level 1 but is not considered Free Software at all because you cannot adapt it to your needs. You can look at the source, and that is about it. Microsoft uses a modified version of Shared Source in their release of the System.Security.Cryptography Code (http://www.gotdotnet.com/team/clr/samples/eula_clr_cryptosrc.aspx). As the name implies, Microsoft's Shared Source Common Language Infrastructure (SSCLI) is also under this license. These are great learning tools, but you cannot use them or modified versions of these products in your product. For instance, you cannot use the SSCLI, which runs on Windows XP, FreeBSD, and Mac OS X to enable your clients to run your .NET applications on multiple platforms in a commercial setting. Open Source SoftwareThe term "Open Source" was created by a group of people who thought that Free Software was too radical a concept to market to most corporations. Obviously, this book focuses on Open Source and freedom levels that allow you access to the source code. This is typically what is meant when referring to "Open Source." Bruce Perens has written a wonderful definition of Open Source on his Open Source Initiative (OSI) Web site (http://opensource.org/docs/def_print.php). In his definition, he outlines ten criteria for Open Source: Open Source LicensesThe OSI Web site lists the accepted Open Source Licenses shown in Table 1.2. As listed in the definition of Open Source, the license must be distributed with the code. It is safest to only use code that uses one of these licenses. Open Source "Free-ness"The FSF has coined a term called Copyleft, which obviously is a play on the word "Copyright," to refer to software that fits their definition of Free Software Freedom Level 3. This means that you are free to use, modify, and distribute code as you see fit, as long as you do not deny this same freedom to the code from someone else. In Figure 1-1 you can see that there is an overlap of Open Source and Free Software. That implies that the FSF does not view all Open Source as free. Of course Open Source software does imply Freedom Level 1 and 2. FSF's Web site categorizes the overlap (see http://www.fsf.org/licenses/license-listl):Copyleft Compatible Licenses
Non-Copyleft Compatible Licenses
Keep in mind that it is fine to use an Open Source Licensed product that is not considered Free Software in your products. You just have to understand the license requirements as well as the goals of your product. Open Source MythsI have found that there are a lot of unjustified claims about Open Source. As I have already mentioned, this topic leans somewhat toward advocacy. Open Source is a hotly debated topic with substantial firepower existing on both sides. Here I will do my best to take an objective look at Open Source so that you can make an informed decision in your Open Source policy, which all companies should have. Open Source Code Is More StableMore eyes do not equal better code. More educated and experienced eyes do mean better code. Cryptography best-practices suggest opening your code for public review. Most often, counterintuitively, this results in more secure code. On the other hand, I will say that with Open Source, most developers want to look good in the eyes of their peers and refine their code to the best of their abilities before releasing it to the public. Recently, Reasoning Inc. (http://www.reasoning.com) compared a few products to promote their Code Inspection Solutions for C and C++. While C and C++ code inspection tools are becoming more and more commonplace, the results of the study are interesting on two levels. First, most of the coding problems found were variable initialization and null pointer problems. These problems are all but eliminated in C#. Secondly, the results in a nutshell are that not all Open Source products are more stable; it just depends on the product. Sorry, no silver bullet here. The first study from Reasoning is comparing the Linux TCP/IP stack against five commercial equivalents. Their findings were that the Linux implementation's bug density is much smaller than even the best of the commercial products. So this proves that Open Source is more stable, right? Not so fast. The same company conducted a study of Apache 2.0 source code. It might shock you to find out that the density of defects in Apache was quite a bit higher than most commercial Web servers. But before you get too hard on Apache, realize that according to Netcraft (http://www.netcraft.com), the first version of their product pretty much runs the Internet (see Figure 1-2). Figure 1-2. Most Common Web Servers according to May 2003 Netcraft Survey. Open Source Code Is More SecureThe CERT Coordination Center (http://www.cert.org) tracks computer security incidents and vulnerabilities and publishes security alerts based on this information to the general public. The rate of increase of security incidents is astounding (see Figure 1-3). Figure 1-3. CERT Security Incident Reports.[View full size image]  Figure 1-4. CERT Security Incidents from 2000-2002. Open Source Code Is CheaperCost is the most controversial subject when it comes to Open Source. Even when you are given something, there are always costs associated with it. If given a free car, you must evaluate if the maintenance costs of that car are reasonable so that you can justify taking it. However, if given a house, you usually cannot go wrong in taking it unless it is in a bad location. These examples are decisions that are somehow easier for most people to make than when it comes down to software. Only time will tell if Open Source and its proponents will outperform proprietary software companies. Just as with cars and houses, Open Source software decisionmaking is going to be unique to every organization. For instance, I accepted cars in high school that I would be embarrassed to drive today. The same is true with software. A struggling startup company might find Mandrake Linux (http://www.mandrake.com) and Open Office (www.openofffice.org) wonderful solutions, whereas a middle-size or larger company may feel safer using a product that has commercial technical support such as Windows and Microsoft Office.NOTE This does not imply that Linux (and other Open Source products) do not have commercial technical support available because most of them do. Nor does this imply that Open Source products are only suitable for small companies, for there are several large companies that depend on Open Source. |
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