As far as I can tell, after 1.7, if a teacher wants to restrict students from adding entries, he has to do it via roles: (http://moodle.org/mod/forum/discuss.php?d=64771)
I think this was not a good change for a glossary.
First of all, our regular instructors would not have the capability to override roles. And most of them would not even want it (too scary for the novice users).
Which means that we will need to create bunch of custom-tailored roles, like "Forum Moderator", "Student without the rights to edit glossary", etc. And if Forum moderator role can be justified, the second one seems to be unnecessary stretch.
Second, ability to change a glossary to "Do not allow student entries", provides possibility to impose a time limit quickly.
Third, overall I believe that we should stick to "legacy" settings in modules where appropriate.
We have those legacy roles, that inherited whatever was good and useful in 1.6. So, I think, that all the tools and modules also should inherit good and easy features. Also, it seems to me, that tools should be really separate from roles, in order to stay modular. And putting one of the core functionalities away, seems like marrying roles and tools too much.
Please let me know what do you think.
I will probably post this at the tracker as a feature request.