GCC is available for free in source form from GNU mirrors (http://egcs.cygnus.com) or in binary form from http://www.sco.com/skunkware. It provides compilers for C, modern C++, Java, Fortran 77, Objective C, and Chill. If you are using OpenServer and don't have the OpenServer Development System installed, you must be sure to install the Linkers and Libraries kit as described in the documentation of the GCC binary kit. On OpenServer, this kit can generate ELF or COFF and defaults to ELF. On UnixWare, it supports ELF only.

The UDK is a next-generation development environment that is an optional product from SCO. It includes C and a modern C++ compiler. It can generate binaries that will run on OpenServer, UnixWare 2, and UnixWare 7 when appropriate runtimes are installed. This is the only available devsys for UW7. It emits ELF only which makes it unsuitable for OpenServer device drivers or generating binaries that run on pre-OpenServer SCO OSes such as ODT.

GCC can be built from source to provide the "universal binary" features of the UDK following the directions in the source distribution. No known binary kits are available at this time. Doing this does require you have a licensed copy of the UDK.
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