Pine does several things very very very well.
e) Is a free open source client.
It appears that Derek is correct - as long as you are reading in a case-sensitive manner. Pine is not Open Source, in that you cannot redistribute a modified version. However, it is "open source", in that the source code is openly available to you for local use and modification.
http://www.washington.edu/pine/faq/legal.html
10.1 Is Pine Open Source?
It depends on how that term is defined. Source for Unix Pine is provided to allow users and system administrators to customize and adapt Pine for their own requirements. UW's Pine license allows anyone to download source code for Unix Pine and make modifications for their own local use without asking permission. Anyone can also create and distribute patch files to implement bug fixes or minor enhancements without asking permission. However, redistribution of a modified version of Pine requires explicit permission from the University of Washington.
10.2 Weren't earlier Pine licenses less restrictive regarding redistribution of modified versions?
No. License wording has changed from time to time, but the owner's intent has not. When it was discovered that some individuals were misinterpreting the intent of the University, the license wording was clarified.
In particular, the earliest Pine licenses included the words: "Permission to use, copy, modify, and distribute this software... is hereby granted," but some people tried to pervert the meaning of that sentence to define "this software" to include derivative works of "this software". The intent has always been that you can re-distribute the UW distribution, but if you modify it, you have created a derivative work and must ask permission to redistribute it. There has never been implicit or explicit permission given to redistribute modified or derivative versions without permission. The license wording was therefore changed to clarify this point.
