I have two web applications living on the same Tomcat installation, in which I would like to implement Quartz 1.x such that each web app only serves a single jobgroup in a shared Quartz data store.
Is it possible to configure a Quartz instance to serve (or ignore) specific group set?
No, but you can create multiple quartz instances, and only put certain job groups in each (and then it will of course only fire certain job groups).