I raised this same question in another forum ("How do I..." in the course, "teachers using moodle" in facultyroom.org) and the answer is no, glossaries do not allow groups. There is a technical reason for this having to do with slowing down the software too much - you can read all about it in the other forum.
To accomplish something very similar to what you want to do, I have elected to have different groups create their own wikis (which do allow groups) in which they define terms or concepts. It doesn't have the nice alphabetical search that a glossary does, but I came up with a main page that will serve as an index. My plan hasn't met live students yet, so take this as a suggestion rather than the voice of experience