South Richmond Hill
Do "down" aliens count for determining which column on the alien action chart to use?By a strict reading of the rules, yes, as they're considered active. I usually play that they don't, as this makes the aliens a bit less bloodthirsty (and thus more intelligent in most cases).
What counts as a clear exit?One that could be used to leave the room, regardless of whether there's enough MA left to actually do it. Since a unit entering a square with a hostile unit must stop, fleeing aliens can't safely get out if there's an active human unit on either side of the door.
You can't move through a door diagonally, so really all you have to look for is counters next to the door.
the square adjacent to the door has a down human, a down alien and an active alien. The active alien is trying to flee Is the door clear?Yes, although admittedly this isn't clear in the rules. The Terrain Effects sentence on this should read:
If a unit enters a square with an active hostile unit, the unit must stop.
Oddly enough, like the alien claw issue this question hasn't come up in the 20 years since the game was originally published. It's a good item for Andrew to add to the errata page.
What if there are active humans on the other side of the door?Then it's blocked. If there's another exit, the alien will use it, otherwise the guy leaning on the door is likely in for some serious hurt.