I'm about to start the Brute Force side mission.

The mission sas rebels control the Wokkies as allies at no cost. Does that mean the Rebels can not use Luke as their one ally, or do the Wokkie not count since they haven't earned them?

Thanks for the help

It doesn't count towards the up-to-one ally limit.

The Wookiee Warriors are provided by the setup (and does not give threat to the imperial player), so the rebels can still choose to take one ally they have earned to the mission (which gives the imperial the corresponding amount of threat and an optional deployment).

The mission has to say that the rebels can't bring an ally. I think there might be one like that if I recall correctly. If it doesn't say it, then you can always bring an ally regardless how many you might start with. We had R2D2, C3P0 and Leia on the droid's reward mission (Leia was the only one we added ourselves)

As far as I can tell Captured is so far the only mission where the rebels can't take an ally (as specified in the special setup section). (I don't think Jabba's wave has one of these, but may be mistaken.)

There are other missions where the rebels cannot choose to take a certain ally to a mission because that ally may appear in that mission naturally through mission events. Usually I don't read that part of the rules unless the rebels have actually earned that ally, but that's my house rule.

Thanks for all the help