SqCVS is a clean implementation of the CVS pserver protocol in Squeak.
It is written on top of SocketStream - the highlevel Socket wrapper that was first created in the Comanche/KomHttpServer package and that is now included in the newer standard Squeak images.
SqCVS has no UI and it still doesn't know how to do "add" and "remove". But it knows how to do pretty much of the CVS protocol.
Newer versions are only verified to work with Squeak 3.9 and unless someone asks me I will stick to supporting 3.9 as of now.
If you wish to use it in Squeaks older than 3.9 you should be fine if you install FastSocketStream and change the single reference in class CVSSocket to that instead of SocketStream.