Open Source & Derivative Works
WordPress & the GPL
ProCD v. Zeidenberg
USL v. BSDi
Shrink Wrap License
MS Community License
MS Permissive License
Open Source Software ("OSS") is computer software for which the source code is made available, and for which it is usually (some exceptions, rules and restrictions may apply) permitted to study, modify and improve the software. Additionally, users are also normally permitted (again, exceptions, rules and restrictions may apply) to distribute the software in modified or unmodified form.
Open Source is not a trademark, so while most people used the term in broadly the same way, sometimes you may find that software described as "Open Source" is actually being distributed on a different licensing basis, etc. To reduce the possibility of confusion, the Open Source Initiative developed a set of 10 criteria (OSD) for Open Source licenses, and those licenses which have been verified as satisfying those critera may be described as OSI Certified.
Closely related to Open Source is Free Software, as defined by the Free Software Foundation. Free Software is software that is licensed so as to provide the following four freedoms (numbered from zero), and for which access to the source code is considered a precondition (in particular a precondition for freedoms 1 and 3):
An important point to note about both Open Source and Free Software is that with the exception of public domain software (which is sometimes classified as a subtype of Open Source or Free Software), the software is copyrighted, there are terms and conditions which apply, and that using or distributing the software in violation of the terms and conditions is almost certainly copyright infringement.
The information in the Open Source section of this web site includes: