The DB Software Package is written in highly portable C, and (with the exception of a few MS-DOS or UNIX-specific display or data-acquisition programs) should be easy to compile with any K&R or ANSI C compiler. The UNIX and MS-DOS make description files (Makefile and makefile.dos in software/db and in each of its subdirectories) should get you started.
Notes for Macintosh users can be found in software/MAC.TXT, and in software/db/MAC.TXT. These include detailed instructions for compiling the DB library using Symantec's Think C. Since most of the applications are command-line oriented, they will require minor modifications to run under the Mac OS.