traditional model of selling copies of Free Software distributions.

Many companies make substantial revenue

from this model. Some choose this model because they have

found that for higher-end hardware, the profit made from proprietary

software licensing fees is negligible. The real profit is in the hardware,

but it is essential that software be stable, reliable and dependable, and

the users be allowed to have unfettered access to it. Free Software, and

GPL'd software in particular (because IBM can be assured that proprietary

versions of the same software will not exist to compete on their hardware)

is the right choice.

For example, charging a ``convenience fee'' for Free Software,

when set at a reasonable price (around \$60 or so), can produce some

profit. Even though Red Hat's system is fully downloadable on their

Web site, people still go to local computer stores and buy copies of their

box set, which is simply a printed version of the manual (available under

a Free license as well) and the Free Software system it documents.

\medskip

Custom support, service, and software improvement contracts

are the most widely used models for GPL'd software. The GPL is

central to their success, because it ensures that the code base

remains common, and that large and small companies are on equal

footing for access to the technology. Consider, for example, the GNU

Compiler Collection (GCC). Cygnus Solutions, a company started in the

early 1990s, was able to grow steadily simply by providing services

for GCC --- mostly consisting of new ports of GCC to different or new,

embedded targets. Eventually, Cygnus was so successful that

it was purchased by Red Hat where it remains a profitable division.

However, there are very small companies that compete in

improve it for everyone. Meanwhile, companies who rely on GCC for their

work are happy to pay for improvements, and for ports to new target

platforms. Nearly all the changes fold back into the standard

versions, and those forks that exist remain freely available.

\medskip

\label{Proprietary Relicensing}

A final common business model that is perhaps the most controversial is

proprietary relicensing of a GPL'd code base. This is only an option for

software in which a particular entity holds exclusive rights to

relicense.\footnote{Entities typically hold exclusive relicensing rights

  either by writing all the software under their own copyrights, collecting

  copyright assignments from all contributors, or by otherwise demanding

  unconditional relicensing permissions from all contributors via some legal

  agreement} As discussed earlier in this tutorial, a copyright holder is

permitted under copyright law to license a software system under her

copyright as many different ways as she likes to as many different parties as

she wishes.

Some companies use this to their

financial advantage with regard to a GPL'd code base. The standard

version is available from the company under the terms of the GPL\@.

However, parties can purchase separate proprietary software licensing for

a fee.

This business model is at best problematic and at worst predatory because it means that the GPL'd code

base must be developed in a somewhat monolithic way, because volunteer

Free Software developers may be reluctant to assign their copyrights to

the company because it will not promise to always and forever license the

software as Free Software. Indeed, the company will surely use such code