All of the applications are written in C.
As the software has been written to the requirements of DEC C (in an uncritical, VAXC-backward-compatible compilation mode, i.e. /STANDARD=VAXC (when moving from VAXC C to DEC C the author discovered he wasn't the rigorous software engineer he had hoped he was :^)) its build and run-time behaviour in other compiler environments is unpredictable.
All applications are linked against the DEC C DECC$SHR.EXE RTL. The DEC C run-time environment is prefered to the VAX C run-time environment because the former's greater integrity and improved performance over the latter. See the section Executables for further information on this component. In all probability, if you're considering re-compiling, this environment will already be available on your site somewhere.
Brute-force build procedures are provided in each software application source directory. They are named ``BUILD_whatever.COM''.
Two procedures can be used to rebuild or relink all applications in the package. Because of some dependencies the HTTPd server should be built first.
Also, the HTTPd server itself is specifically tailored to Digital TCP/IP Services for OpenVMS (primarily) and NETLIB (a close second). The HTTPd server build procedure needs to be told to explicitly build for NETLIB. The executable in this case is specifically named HTTPD_NETLIB.EXE.