Answer
If a certain key-performance indicator (KPI) exists on a device (that is, if you can issue a show command to obtain the KPI), then OpenNTI (an open-source universal collector) can collect the KPI from the device. This capability is not restricted to Junos QoS. OpenNTI collects every KPI available in Junos. It can be run on all platforms because the interaction is through the shell or NETCONF.