In the GNU project, when we speak of "free software", this refers to liberty, not price.  Specifically, it refers to the users' freedom to study, copy, change and improve the software.  Sometimes users pay money for copies of GNU software, and sometimes they get copies at no charge.  But regardless of how they got the software, or whether it was modified by anyone else along the way, they have the freedom to copy and change it--those freedoms are what "free software" means.

                                                                                                                    --- RMS

当我们在GNU项目中提到『Free software』的时候，它是指自由，而不是价格。它尤其意味着用户可以自由的学习、复制、修改和改进软件。用户有时花钱购买GNU的软件，有时免费获得，不管他们通过什么方式获得这些软件，或者这些软件是不是已经被其他人通过同样的方式修改过了，他们都可以自由的复制和修改它。这种『自由』就是我们所说的『Free software』的含义。