We use it all the time and it's nice !
Since Richard Wesley, the author, is American, you'd better go directly to http://www.electricfish.com/hawkfish/CWCVS/CWCVS.html for a good explanation in plain English...
Only the Mac side is provided right now and it is a shareware.
Right now, two MPW tools are provided with MacCVS with complete source code :
Place these tools into the tools folder of MPW.
To get the usage of these tools, simply type the command + enter.
All you need after is to read how to set-up environment variables for cvs, then you can use it straight. Most of the time you don't even need to set any variable because cvs keeps track on your disk about the informations it needs.
Important note : these tools require to find the shared library provided with MacCVS. So you can place the shared library in the system folder or create two aliases of thse libraries at the same directory level than the mpw tools.