weening@Gang-of-Four.Stanford.EDU (Joe Weening) (09/29/87)
[I've added comp.text to the distribution of this message, and removed
comp.sys.atari.st.]
Yesterday I showed Don Knuth a copy of Brandon Allbery's message, and he
provided the following reply:
I intend to exercise my right of copyright only (and vigorously)
to the extent of denying the right to use the name TeX unless the
TRIP test has been passed and there are no extensions to the
language. The bit about not changing the file is for the WEB
version, not a derivative in another language ... but any changes
must preserve the TRIP-test validation.
This didn't completely answer the question as I understood it, so we had
a further exchange of messages as follows. (Text in brackets is mine.)
[JSW:]
Brandon Allbery asked whether he was prevented from running the
Pascal source of TeX through a Pascal-to-C generator. My
interpretation of this is that it is OK, since Pascal-to-C plus a
C compiler is equivalent to a Pascal compiler. As long as the
result passes the Trip test, it can use the name TeX. Do you
agree?
[DEK:]
Yes. (I don't believe there exists a valid Pascal-to-C translator
in the world, so the TRIP part is very important! Even Lyle
[Ramshaw]'s Pascal-to-Mesa translator had lotsa problems, and I
know DRF [David Fuchs] had to do a lot of handwork to get around
bugs in the translators he used.) (Also, TeX has found at least
one bug in every Pascal compiler it's been run on, I think, and at
least two in every C compiler...! So the code sometimes must be
patched to get around these system bugs.
The code is in the public domain. Anybody can copy it and change
it in any way if they don't call it TeX. If they want to call it
TeX, it's OK if they rewrite it in C or Ada or LISP or whatever,
as long as they don't add any extensions and as long as they pass
the TRIP test. My note in the program says that I don't want the
WEB files to be changed by anybody, because WEB has a better way
to make changes. As you know, the master WEB file still gets
updated sporadically...
The following is my opinion based on the above and experience with TeX,
so don't take it as being as "official" as the above comments.
(1) Don Knuth's main concern is that the TeX name not be applied to
anything that differs in a noticeable way from the WEB implementation.
Any program that passes the TRIP test and does not extend the language
may call itself TeX, but nothing else may.
(2) His WEB version of TeX is public domain. Now it seems that this
is contradicted by the copyright, but he clearly has chosen not to
exercise all of his rights. (I believe you can find published
statements similar to those above in TUGboat, the newsletter of the
TeX User's Group, but I haven't checked.)
(3) In addition to waiving the right to make copies of the WEB code,
Knuth has waived the right to make derivative works. In fact, I'm
sure that he encourages translation of TeX into any language if it
makes it possible to run on new systems, or improves its performance.
Many people have already done this. If you use WEB, you should use
the change-file mechanism rather than editing the main source file.
In summary, if you make changes in order to get TeX to work correctly,
you're in no trouble. And if you want to use the WEB code for TeX or
pieces of it in other programs, not called TeX, you're also free to do
so. Just don't use the name TeX unless your version passes the test.
Joe Weening
Internet: JSW@SAIL.Stanford.EDU