I'm just a committer like you.
I see this ticket depends on INFRA-7738
that mentions BuildBot so I can share with you how Apache Wicket project does this.
you can see our BuildBot config. I see openjpa.conf in the same directory.
All you need to deploy -SNAPSHOT versions is to do: "mvn deploy". I guess OpenJPA's pom.xml uses the Apache parent pom:
this is enough for Maven to realize that -SNAPSHOT versions should be deployed at https://repository.apache.org/content/repositories/snapshots