"JBOC" is an analogy to JBOD. This directory covers various techniques that allow you to run scripts across a large number of computers, when the computers are tied together more loosely than a computer cluster. Related concepts are jungle computing and grid computing.
In particular, each node has no specialized software installed on it, software that would normally be found on clusters (eg. no network monitoring agents, or any other agent or daemon whose main purpose is to coordinate work with other nodes.
Often, the only interface available on nodes is an SSH daemon. Often, Expect (or Expect-like tools) are used heavily.