The passwords are the flags. The Slack link on that page is down, but you don't need it. Use the initial credentials below.
The initial credentials for the Century game are:
Username: century1
Password: century1
The initial credentials for the Cyborg game are:
Username: cyborg1
Password: cyborg1
Posted 6-4-2020
Link updated 2-23-21
Minor updates 6-10-2021
Initial credentials added 6-20-23