You've said that GNOME is Free Software. What does Free Software mean?
Most software licenses are designed to limit the users freedom to use, examine, modify and distribute the software. In the GNOME project, and the Free Software community in general, we believe that such restrictions are unethical, and we endeavor to produce quality software that is free of such restrictions. This is what we call Free Software. Traditionally, it has referred to software which allows three types of freedom:
The freedom to study how the program works and adapt it to your needs.
The freedom to redistribute copies so you can share with your neighbor.
The freedom to improve the program, and release your improvements to the public, so that the whole community benefits.
More recently, a fourth freedom has started being restricted by licenses, the freedom to use the software. Since software licenses are based on copyright law, and copyright law only addresses distribution, not use, we assumed that freedom of use goes without saying. Suffice it to say that while freedom of use is not part of the traditional definition of Free Software, the concept does include that freedom.
 | If the following paragraph is hard to understand in translation, forgive me. Unlike most languages, in English the word used in both "free beer" and "free speech" is free. This causes some confusion when discussing Free Software. |
Free Software is a matter of liberty, not price. To understand the concept, think "Free Speech" not "Free Beer". The Free Software community is not at all against the concept of selling copies of software, or programmers making a living. We are not against commercial software, we are against proprietary software. For more information, check out the articles at http://gnu.org/philosophy.
In the GNOME project, we protect the user's freedom by using the GNU General Public License (GPL) and the GNU Lesser General Public License (LGPL, formerly known as the GNU Library GPL). These licenses are carefully designed with legal advice to produce a "copyleft". That is a copyrighted work that guarantees that it will always be freely redistributable. This is by making sure that modifications and derivative works are also covered under the GPL.
The main GNOME applications (and a few of the libraries) are covered under the GPL. Most of the core GNOME libraries use the LGPL, to allow other free (and proprietary) software licenses to be used when making GNOME software, while still protecting the libraries from being restricted.