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NTS (TeX reimplementation in Java from 2001) still compiles under Java 16
GitHub copy of the NTS/TeX source code from 2001. Contribute to jamespfennell/new-typesetting-system development by creating an account on GitHub.
However, for various reasons it was decided not to continue the project (i.e., support more modern flavors of TeX), and there has been no further development on this code since. A good place to start is Knuth's own plain TeX format; compiling plain.tex from that page yields an actual document! The code as hosted here has small modifications versus the original that are fully detailed in the changelog.
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