The article author claimed they got their landlord's permission first, so I doubt they'll be taking it down when the landlord comes over. They'll just take it down when they move out.
Also... I lived in rented apartments for more than 15 years, and the only time a landlord entered my unit was one time when I explicitly asked her to (there was a water leak, and I was about to leave town and wouldn't be around to let the workers in to fix it). Is this a normal thing? Are landlords constantly visiting their tenants?