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 like CodeSourcery, as well as

other medium-sized companies like MontaVista and OpenTV that compete in

this space. Because the code-base is protect by GPL, it creates and

demands industry trust. Companies can cooperate on the software and

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 is the sole copyright holder. 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.

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.

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

contributions in proprietary versions licensed for fees.

\section{Ongoing Compliance}

GPL compliance is in fact a very simple matter -- much simpler than

typical proprietary software agreements and EULAs. Usually, the most

difficult hurdle is changing from a proprietary software mindset to one

that seeks to foster a community of sharing and mutual support. Certainly

complying with the GPL from a users' perspective gives substantially fewer

headaches than proprietary license compliance.

For those who go into the business of distributing {\em modified\\}

versions of GPL'd software, the burden is a bit higher, but not by

much. The glib answer is that by releasing the whole product as Free

Software, it is always easy to comply with the GPL. However,

admittedly to the dismay of FSF, many modern and complex software

systems are built using both proprietary and GPL'd components that are

not legally derivative works of each other. Sometimes, it is easier simply to

improve existing GPL'd application than to start from scratch. In

exchange for that benefit, the license requires that the modifier give