TeX dates from the 1970s yet is still in everyday use — few pieces of software have survived so long, so stably. This page tells how TeX came to be and where it is heading, and explains exactly what “free and open” means for its licensing.
How TeX came to be
TeX was created by Donald E. Knuth (b. 1938) of Stanford University — a towering figure in computer science, recipient of the Turing Award (1974) and the Kyoto Prize (1996).
The spark was his own *The Art of Computer Programming*. When the revised second volume was set by computer, the result looked markedly worse than metal type — and Knuth, unwilling to accept that, resolved in 1978 to build software that could typeset as beautifully as letterpress. He even wrote METAFONT for designing type and designed the Computer Modern typeface himself. TeX in essentially its present form was finished around 1982, and *The TeXbook* followed in 1984.
A version number that converges to π
From 1989 Knuth turned from extending TeX to stabilizing it. Since version 3 it uses an idiosyncratic scheme: each fix appends another digit, so the number creeps toward π — 3.14 → 3.141 → 3.1415 …. Knuth’s wish is that at his death the number be set to π and frozen forever, with no further changes no matter what (its sibling METAFONT heads toward e).
This relentless commitment to stability is why a manuscript written decades ago still compiles unchanged today. TeX has become something like a fixed point in the history of computer typesetting.
LaTeX, past and future
LaTeX was written by Leslie Lamport in the 1980s. The current release, LaTeX 2ε (1994), is what “LaTeX” now means (the older one was LaTeX 2.09). Its internals are gradually being replaced by the next-generation LaTeX3 (expl3) code, so in the future some “ill-behaved” documents may stop compiling.
The TeX engine itself keeps evolving, too: successors like pdfTeX, XeTeX, and LuaTeX added direct PDF output, Unicode, and system-font support. See the “Engines & formats” pages for details.
Licensing — free and open
Both TeX and LaTeX are open source and free to use, including commercially. A few conventions are worth knowing.
- TeX itself. You may even sell a value-added version. But you must not call something “TeX” unless it is fully compatible — pTeX, for instance, does not call itself “TeX.” In the US the TeX trademark is held by the American Mathematical Society (AMS), purely to stop unrelated parties from registering it; you do not need to add any “TeX is a trademark” notice when you use it.
- LaTeX. It follows the LPPL (LaTeX Project Public License). You may redistribute modified versions, provided you rename the file — so a modified file cannot be mistaken for the original.
- Japanese pLaTeX, etc. Originally from the former ASCII Corporation, these have moved to a community edition by the Japanese TeX Development Community, under a (modified) BSD license: modify and redistribute freely as long as the copyright notices remain.
All of these — the TeX license, LaTeX’s LPPL, and BSD — meet open source in the sense of the official Open Source Definition.