There is a workaround how to get cvs without all unneeded stuff from xcode. I used it and I have what I need.
1. Install Xcode. Doesn't matter which version. You don't need to download 4.1 form App Store. You can use Xcode package from Snow Leopard instalation disk. It is much smaller than 4.1.
2. Copy cvs file to one of our folder in including path (in. ex. /usr/bin):
bash$ sudo cp /Developer/usr/bin/cvs /usr/bin
3. Remove Xcode:
bash$ sudo /Developer/Library/uninstall-devtools --mode=all
After all we can use cvs from the command line as usual and many gigabytes free. Of course setting CVSROOT env variable will be very helpful, but I'm sure everyone knows how to use cvs.