Introduction: BOSS is a DCL clone and more.
I've just recently begun looking at BOSS. The first thing you'll notice is the source are mostly ".p" files. According to README.intro this a "LIB$TPARSE surrogate". It is translated to C by the "gt" program which I think is supplied in parser.tar.gz.
Compiling parser.tar.gz: `make CC="gcc -ansi"' worked for me on Red Hat Linux 5.0 (-ansi is to deal with the fact that there is a variable named "inline"). I had to edit parser/Makefile to comment out the reference to -ldgc; apparently this is for Data General Unix (or is otherwise unnecessary). There were various warnings which I ignored. This gave me an executable called "GenTable", which I copied to "gt". When I tried to run it (from the cld.tar.gz Makefile), I got a "Parsertabelle 'ParserDef.t' nicht gefunden" error. Despite appearances, this does not seem to be related to a file named "ParserDef.t". It would seem to be some cause internal to GenTable, specifically in Parser.c (loadpcb). That is about as far as I got....
There are some suggestions from Jouk Jansen; it would appear that he is running into roughly the same problem that I did.
Note that there is another program out there called BOSS, at ftp://ftp.wku.edu/vms/fileserv/boss.zip. I am looking at version 5.1 dated 25 Sep 1996. It is an unrelated program to the BOSS DCL clone (it is an interactive job controller, in general terms similar to the job control features found on unix).