A.3. Licenses
Although
some commercial software has been mentioned, this book has
overwhelmingly focused on freely available software. But
"freely available" is a very vague expression that covers
a lot of ground.
At one extreme is software that is released without any restrictions
whatsoever. You can use it as you see fit, modify it, and, in some
cases, even try to sell your enhanced versions. Most of the software
described here, however, comes with some limitations on what you can
do with it, particularly with respect to reselling it.
Some of this software is freely available to some classes of users
but not to others. For example, some software distinguishes between
commercial and noncommercial users or between commercial and academic
users. For some of the tools, binaries are available, but source code
is either not available or requires a license. Some of the software
exists in multiple forms. For example, there may be both free and
commercial versions of a tool. Other tools restrict what you do with
them. For example, you may be free to use the tool, but you may be
expected to share any improvements you make.
You should also be aware that licensing may change over time. It is
not uncommon for a tool to move from the free category to the
commercial category, particularly as new, improved versions are
released. This seems to be a fairly common business model.
I have not attempted to describe the licensing for individual tools.
I am not a lawyer and do not fully understand all the subtleties of
license agreements. Different licenses will apply to different
organizations in different ways. In some cases, such as when
encryption is involved, different countries have laws that impact
licenses in unusual ways. Finally, license agreements change so
frequently, anything I write could be inaccurate by the time you read
this.
The bottom line, then, is that you should be sure to check
appropriate licensing agreements whenever you retrieve any software.
Ultimately, it is your responsibility to ensure that your use of
these tools is permissible.
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| A.2. Generic Sources |  | A.4. Sources for Tools |
