The source distribution is intended primarily for UNIX systems. Some people have been successful in porting it to other systems as well.
The latest source version is RCS Version 5.7. It is available in compressed tar format (401K) or uncompressed tar format (955K).
The latest PC (OS/2 DOS Win95 NT) binary version is available as three ZIP files. They are rcs57pc1.zip (1.2MB), rcs57pc2.zip (0.9MB) and rcs57pc3.zip (0.9MB). They contain everything you should need to use RCS on a PC. If you want to try to compile RCS on a PC, you will need the supplementary source file (41K). This contains diffs relative to RCS 5.7 and diffutils 2.7.1 sources.
If you have problems fetching the files with HTTP, you can use FTP to fetch the necessary files from the RCS FTP site.
UNIX style man(ual) pages are included in the distributions. There is some additional documentation available on-line. The first is a modified version of the paper that appeared in Software Practices & Experience, July 1985. It is available in PostScript (138K) or *roff (55K). If you want to *roff format, but don't have the pic preprocessor, you need to the pre-piced (63K) version.
The second document is a one-page summary describing the functions of RCS. It is available in PostScript (9K) or *roff (3K).
Aaron Hawley (Aaron.Hawley@uvm.edu) has made HTML and DocBook XML versions of the SP&E paper available online.
The third document is a book written by Brian O'Donavan while at Digital Equipment Corporation. It was never published, but he gave it to Purdue to see if there was any interest from RCS users. It is a compressed tar file (248K)
O'Reilly & Associates, Inc. also published Applying RCS and SCCS by Don Bolinger and Tan Bronson.
If you cannot get help anywhere else, you can send mail to the RCS-BUGS address. This is a mailing list of people that can either answer your question or direct it to the actual code developers.
Applied Computer Sciences offers their /BriefCase 3 Toolkit for free under the GPL, and promotes it as a true client/server solution for UNIX, providing better project management than CVS.
PRCS is supposed to be a much simpler CVS-like tool.
BitKeeper is a fully distributed source management system from BitMover, Inc. It is based on their version of SCCS and is file format compatible with AT&T SCCS.
Aegis is a transaction-based software configuration management system.