The blog Bad Vista puts a nice perspective on the difference in attitude between free and proprietary software:
As the GPL preamble says:
The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software–to make sure the software is free for all its users.
In contrast, a typical Microsoft Vista EULA says:
The software is licensed, not sold. This agreement only gives you some rights to use the software. Microsoft reserves all other rights. Unless applicable law gives you more rights despite this limitation, you may use the software only as expressly permitted in this agreement. In doing so, you must comply with any technical limitations in the software that only allow you to use it in certain ways.
See the difference in attitude?