We've gotten to the bottom of the CVS and Emacs problem whereby a file
would be marked read-only in Emacs, even if you have the correct group
permissions to write to the file (but you weren't the file owner). You
would then have to chown the file if you wanted to edit it.

In a nutshell, the problem arises because CVS and Emacs
version-control mode considers a file locked if there are any
modifications since its last checkout.

When the file owner has made changes to the file but not done a cvs
commit on it, it is out of synch with the latest version in the CVS
repository. At that point, if someone else tries to open the file in
Emacs (which goes to CVS mode automatically), the mode has a feature
whereby it considers the modified and uncommitted file locked. If you
then try to toggle the file writable (C-x C-q) it will prompt you to
add a checkin comment, and then commit the file.

Another situation where you'll encounter a locked file is if you are
not the file owner, but when you open the file, it is still identical
and in synch with the latest version in CVS. You make some changes,
save the file (without committing to CVS), and then close the file.
When you try to re-open the file, it will be locked.

Taking advantage of this behavior, when you encounter a locked file,
that may mean either someone is still making changes on it, or they
forgot to check it in. Check with your colleagues to find out - you
might save some headaches later. And if you lock yourself out, chown
the file, or commit the changes.

In general let's commit changes often, which is a good habit.