Can unsubscribed Guildies Use the Companion App?

Was wondering since a guildie had asked me!
If they dont have an active subscription, can they still use the Companion App to talk in guild chat? Can they use it to chat in guild chat, community chat, and for the mission table? This has been sort of confusing for them. Since I dont let my sub lapse, i dont have any answers but hope some have answers to share here!