Q:
claiming a hall and ftp members?
Captain Commander of a Sky Edge Piracy
A:
They can’t claim it. They need to go to the area in HoT where you claim. They can however enter the hall.
The answer to your question is No they cant help since they dont have heart of thorns expansion as free to players or even vanilla game buyers were the actual hall need to be recaptured.
As maniamsmart said they can enter it after you other guys have claimed it tho.