Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Open source software is being taken seriously as a viable alternative to expensive proprietary applications but it's important to realize that, like its commercial brethren, it comes with a license for use. It's also important to remember that all open source licensing is not created equal.
Free software licensing is quite complex and I recommend browsing gnu.org for the most up-to-date and complete information. According to Eran Strod, director of product marketing at Black Duck Software, around 70% of open source code is licensed under the GPL, something you'll want at least a passing familiarity with.
Although the GPL is popular, it's not the only game in town.