Installing any AMQ feature, whether activemq-client, activemq-broker or activemq-camel, ends up installing the activemq-osgi bundle which is a one-stop-shop include-all bundle for AMQ.
In other words, if you install activemq-client you end up with a fully fledged broker. If you install activemq-camel, you also end up with a fully fledged broker.
Moreover, the AMQ Camel component is part of the activemq-osgi bundle, which means that you can no longer upgrade only the AMQ broker if you're running in a setup with Camel, because it drags along an updated Camel AMQ component which may require newer Camel APIs.
At least it's not possible via Karaf features. A workaround may be to fall back to installing individual AMQ bundles.