I believe Camel-JPA feature should mark openjpa bundle as a dependency becasue it conflicts with open-jpa 2.3.0.
Currently camel-jpa feature.xml defines:
and should be <bundle dependency="true">mvn:org.apache.openjpa/openjpa/2.2.2</bundle>
This problem apears when you have openjpa 2.3.0 installed and with to install camel-jpa 2.12.3 feature.
Not marking the bundle as a dependency results in camel-jpa pulling the OpenJPA 2.2.2 bundle even if karaf has OpenJpa 2.3.0. Since both bundles try to register a PersistenceProvider in OSgi, the second one fails and the bundle fails to start - so camel-jpa feature is not installed.