cvsd is a wrapper program for cvs in pserver mode. It will run 'cvs pserver' under a special uid/gid in a chroot jail. cvsd is run as a daemon and is controlled through a configuration file. It is relatively easy to configure and tools are included for setting up a rootjail.
This server can be useful if you want to run a public cvs pserver. You should however be aware of the security limitations of running a cvs pserver. If you want any kind of authentication you should really consider using secure shell as a secure authentication mechanism and transport. Passwords used in cvs pserver are transmitted in plaintext and this wrapper won't change that.
This server adds a layer of security to cvs. cvs is a very powerful tool and is capable of running scripts and other things. By running cvs in a rootjail it is possible to limit the amount of "damage" cvs can do if it is exploited. It is generally a good idea to run cvsd without any write permissions to any directory on the system.