Living things can pass without problem. Dualnatured things on the other hand are excluded (spirits and active foci), as well as spells and spell like critter powers.
The creator can cast through the barrier at will. It only extends to the mundane or the astral, so summoning spirits isn't affected (those appear in the astral and can than move inside). Likewise, Adept powers can pass through without problems.
The shadow spirits can of course go back into astral, move in our midst and materialize, but then they can't just fly out of reach and we have a chance to hit them while they materialize.
I assume, that we all are within the radius of the barrier with Rick at the center after we spend some movement.