I don't know whether something was ripped off or not, because human mind works in a similar fashion and synchronicity is possible (when two or more individuals or groups come to the same solution or idea independently), but some similarities on display here are striking. As someone has said, Death Star looks similar to Apokolips, observed from the distance. As no one has said (or I missed that, in which case I apologize), the relation between Luke Skywalker and R2D2 is similar to Orion and Mother Box - she is artificial and helpful; they fly together; she sounds "ping, ping, ping" and he understands what she's saying. "May the Source be with you" - those who die return to the Source. Etc, etc... many other similarities are already mentioned. Some of those ideas are much older than Lucas or Kirby, of course, but there are too many connections of this kind, in concepts and iconography rather than plot elements - far more than with any other single work of fiction mentioned (including Flash Gordon) - that it's simply fascinating, at least.