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Software is like a car

Proprietary software is like a car with the hood welded shut. Open source has several complex implications.

This analogy illustrates the key distinction between free software and open source, and some implications of open source and software licenses.


Source code is like opening the hood

In many ways, software is a lot like a car. If you're like most people, you don't want access to the source code. Likewise, most people don't change their own oil. You may pay a mechanic to change your oil, so only the mechanic needs to open the hood. Proprietary software is like a car with the hood welded shut. Only the software company can see what's really happening and make changes.

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Why opening the hood matters

If anyone can open the hood, anyone can compete in the business of changing oil. Perhaps your neighbor is also a mechanic. Your neighbor will change your oil for less money. Now it matters if you can open the hood. Your neighbor may even be a very talented mechanic and wants to make your car go faster. Your neighbor likes to tinker and will upgrade your car for the cost of parts. With proprietary software, this kind of exchange isn't possible.

Some people like fixing cars and improving them. Programmers like fixing computers and writing software. Some mechanics and some programmers enjoy challenges and tinkering, and sometimes do it for free. They are driven by intellectual curiosity.

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Software licenses

Suppose I'm a car manufacturer. I sell you a car under either the GPL or the Mozilla Public License. The GPL is a free software license, while the Mozilla license is a more moderate open source license.

In either case, you can open the hood, take apart the engine, and modify it. You can make a copy of your modified car and give it to your neighbor. Perhaps your neighbor makes even more modifications, and the two of you happily share parts and ideas. You show me your modifications, perhaps at a car show or on your Web page.

Your original car is either a GPL car or a Mozilla car. If you bought the original car under the GPL, I can include your modifications to the new "official" cars I sell, and the new cars must be sold under the GPL. My new customers can still open the hood, etc.

This isn't necessarily true if you bought the original car under the Mozilla license. On the new cars I sell, I can include your modifications. Furthermore, I can weld the hood shut. You and your neighbor can still tinker with your late-model cars, and even sell any copies you make. But I've taken your innovations private; I've made them part of my secrets.

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Implications

Of course, software programs are not like cars. Bruce Perens reminds us that, "There is very little cost associated with copying a piece of information like a computer program. ... In comparison, you can't copy a loaf of bread without a pound of flour." (Perens, in Dibona, p. 172) And you can't copy a car without metal and other parts. However, the analogy frames some important questions about open source software:

  1. Why would you work hard on modifying your car, then give that information to your neighbor for free?
    See: "The Internet and the Bazaar" and "The open source community"
  2. Why would you let me see your modifications if I can weld the hood shut on my new cars?
    See: "The open source community"
  3. Why would your neighbor ever buy from me, if you'll give him a copy of your car for free?
    See: "Total cost of ownership (TCO)"
  4. What happens to my company and my employees if you start giving away copies of our product? See: "Evil software"

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