This is the AT&T Software Technology (AST) toolkit from AT&T Research. It includes many tools and libraries, like KSH, NMAKE, SFIO, VMALLOC, VCODEX, etc. It also includes more efficient replacements for a lot of the POSIX tools. It was designed to be portable across many UNIX systems and also works under UWIN on Microsoft Windows (see UWIN repo on GitHub under att/uwin).
This software is used to build itself, using NMAKE. After cloning this repo, cd to the top directory of it and run:
./bin/package make
Almost all the tools in this package (including the bin/package script are self-documenting; run --man (or --html) for the man page for the tool.
(If you were used to the old AST packaging mechanism, on www.research.att.com, this repo is equivalent to downloading the INIT and ast-open packages and running: ./bin/package read on them).