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TEX itself

We have modelled our policies on those of the TEX system since this has for some time now been widely acknowledged as a very stable and high quality typesetting system.

The distribution policy set up by Donald Knuth for TEX has the following features:

- There is a clearly specified method for changing parts of the software by the use of `change files'.
- Although arbitrary changes are allowed, the resulting program can be called TEX only if its functionality is precisely the same as that of TEX (i.e. neither less nor more) in all important areas.
- There are many files in the system that cannot be changed at all (without changing the name): examples are the file `plain.tex` and the files associated with fonts, including the Metafont source files.