This website does not have expensive, sophisticated scaling behind it, and it will only be able to handle so many simultaneous users and downloads. To give all users a fair chance to browse and download titles, an Acceptable Use Policy is in place which all visitors are required to follow.
The primary rule is no bots, site scrapers, or agressive download managers. You are free to browse the site as much as you like, and use well-behaved download managers to assist in downloading. But attempting to use automated tools to search and download large portions of the archive is disallowed.
Some request rate limits are in place to give all visitors a fair share of the server bandwidth. An individual IP address will be rate-limited browsing the website, and will be limited to 8 simultaneous downloads. The server operator will review server usage from time-to-time and may change the rate limits to optimise server load and visitor experience.
The second rule is no attempting to evade limits and restrictions. The use of multiple IP addresses and VPN connections to circumvent IP rate-limiting is disallowed.