[Beowulf] no shared state, shared state with explicit locking, shared state without explicit locks

[John Hancock]

Just ran across this piece of advice on slashdot:

"I'm not familiar with all of those libraries mentioned in the story,
but I'll bet that those three classifications (no shared state, shared
state with explicit locking, shared state without explicit locks)
probably cover the models used by most if not all of them. If you
understand the trade-offs in those, you can produce a sensible design,
and then the toolkit or framework you use to code it up is mostly just
an implementation detail." -Anonymous Brave Guy (457657)

A quick google and a search of the mail list archives did not yield
anything that looked like a good explanation of what the differences
are between shared state,  shared state with explicit locking, and a
shared state without explicit locks libraries.

Is Anonymous Brave Guy using unusual terminology for concepts that
usually go by other names?

If anyone on the list would care to share his/her explanation/opinion
about what Anonymous Brave Guy wrote, I'd be most honored.

-j