The Linux abi is a patch to the linux kernel that allows a linux system to run foreign binaries.
This was developed and written by Christoph Hellwig and Joerg Ahrens as a follow on to the iBCS/iBCS2 project written for the older 2.2.x kernel by Mike Jagdis.

Currently supported binaries are:

SCO OpenServer
SCO OpenDesktop
SCO Unix 3.x
SCO Xenix 386
SCO Xenix 286 (with userspace x286 emul)
SCO UnixWare 7
Caldera OpenUnix 8
SUN Solaris 2
System V Release 3 (SVR3)
System V Release 4 (SVR4)
Wyse V/386
ISC Interactive Unix

ONLY THE INTEL i386 platform is currently supported