by default its read only if you dont give it an api key, it can only see public stuff. once you set FLARUM_API_KEY it can write, but only with whatever permissions that key's user actually has. theres also FLARUM_MODE=read which keeps it read only even when a key is set, thats what i run on our main forum. i also made a separate user with limited perms just for the key so it cant touch anything i dont want it to.