The mouse-over description for Maximum Channels on the Edit Trunk configuration page reads as follows:
"Controls the maximum number of channels (simultaneous calls), that can be used on this trunk, including both incoming and outgoing calls. Leave blank to specify no maximum."
Which is misleading as the feature ONLY prevents opening new OUTGOING channels when the limit is reached.
A more apt description:
"Prevents opening new outgoing channels when the maximum number of channels (simultaneous calls including incoming and outgoing) is reached. Does NOT limit the number of incoming channels. Leave blank to specify no maximum."
Of course, optimally having the ability to limit the maximum number of channels altogether or seperately for outgoing AND incoming would be preferred, but a textual update would suffice in the meantime.
Effects ALL versions post 2.1 (may effect earlier but I haven't tested them)