Many software programs, including WordPress, the popular blogging software, are released under open source licenses such as the GPL. When programs are released under an open source license, you are generally allowed to not only use them, but modify them for your own purposes (creating what is known as a “derivative work”), and in most cases, distribute either the original or modified program to others.
Of course there are terms and conditions that apply even with open source licenses. For example, the terms and conditions may specify that when you distribute to others, you must do so under a particular license. The exact terms and conditions vary depending on which particular open source license applies.
In our new video, open source and derivative works, we discuss what is a derivative work of a software program, and what sort of terms and conditions apply to derivative works with three of the most common open source licenses: BSD, the GPL, and the LGPL.