Just discovered it, hope that helps:

UWIN allows UNIX applications to be built and run on Microsoft Windows 7, Vista, XP, 2000, NT, ME, 98, 95 (W7/VI/XP/2K/NT/ME/98/95) with few, if any, changes necessary. UWIN source and binaries are available under the open source at AT&T AST/UWIN open source downloads.

UWIN contains:

• Libraries that emulate a UNIX environment by implementing the UNIX Application Programming Interface (API)
  
• Include files and development tools such as cc(1), yacc(1), lex(1), and make(1).
  
• ksh(1) (the Korn Shell) and over 250 utilities such as ls(1), sed(1), cp(1), stty(1), etc.

Most of the UNIX API is implemented by the POSIX.DLL dynamically loaded (shared) library. Programs linked with POSIX.DLL run under the WIN32 subsystem instead of the POSIX subsystem, so programs can freely intermix UNIX and WIN32 library calls. A cc(1) command is provided to compile and link programs for UWIN on Windows using traditional UNIX build tools such as make(1). The cc(1) command is a front end the the underlying compiler that performs the actual compilation and linking. It can be used with the Microsoft Visual C/C++ 5.X compiler, the Visual C/C++ 6.X compiler, the Visual C/C++ 7.X compiler, the Digital Mars C/C++ compiler, compiler, the Borland C/C++ compiler, and the Mingw compiler. The GNU compiler and development tools are also available for download to UWIN.

UWIN runs best on Windows W7/VI/XP/NT/2000 with NTFS, but will run in degraded mode with the FAT file system, and further degradation with Windows ME/98/95.

Official homepage

AT&T's Research Projects page

Edited June 17, 201214 yr by patchworks

Could this be used to run linux versions of firefox on win98 systems?