This document sets out some history regarding the POV-Ray codebase, the
license that covers its use and distribution, and how the company Persistence
of Vision Raytracer Pty. Ltd. - which currently distributes POV-Ray - comes
into the picture.
POV-Ray is based on DKBTrace, a raytracer originally written by David K Buck
in 1987, and subsequently co-developed by David and Aaron A Collins between
1988 and 1991.
In 1991 David and Aaron made the decision to allow the source code of
DKBTrace to be used as the basis of a new raytracer, which was to be called
POV-Ray. The development of POV-Ray began with David as the first team leader
- also known as 'team co-ordinator', which is the term used today - heading
up a group of programmers who were dialling in to the then-popular Compuserve
online service.
Even at that early stage, the Team's attitude towards the use and re-use of
the source code they produced was clear - an approach that has persisted to
this day and is formalised in the POV-Ray license. This approach is strongly
influenced - and derives from - David's original rules covering his source
code.
In a nutshell (refer to the current license
for the full terms) David allowed DKBTrace (and thus POV-Ray, as it is based
on DKBTrace) to be used freely by end-users, and freely distributed, as long
as it was not sold, included with a commercial program, or used in certain
other ways that contravened the concept of the software being freely available.
He also allowed his source code to be used by other programmers to, for
example, port the program to other platforms, add new features, or create
derivative works (as long as they were fully functional versions of the
original program). However, in order to use the source in this way, the
programmers involved had to agree to his terms, which included the condition
that the modified source code had to be released if the modified program made
from it was released, and that the modifications themselves be placed under the
same license as that which covered the program. This condition meant that the
team co-ordinator could manage the project without having to continually refer
license matters to each contributor.
David Buck has provided a written statement regarding the above, a copy of
which may be read here.
All the code that is in POV-Ray today is the result of one of three types of
contributions:
- David Buck's original contribution.
- Rare and limited instances where authors explicitly granted permission
for pieces of their code to be placed into the DKBTrace or POV-Ray codebase
verbatim, without any need for the original author to otherwise deal with
the existing source.
- Code that has been introduced as a result of a programmer taking a
previously-existing version of the source code and working with it in order
to be able to create the code that they eventually contributed. In order for
them to have been able to do that legally, copyright law requires that they
comply with the conditions placed upon the source that they obtained.
Therefore, it is the position of the current developers of POV-Ray that the
team co-ordinator, by virtue of the above, has the right to administer the
entire POV-Ray codebase under the terms of the POV-Ray license.
