This is reg.i2p registry service.

Service is Up. Hosts check is done every hour.
Supported commands:

For addressbook subscription use /hosts.txt file.
The link returns basic addressbook upon initial request or request with no If-Match-None header.
Following requests will return full alive hosts list.

Static links to lists:
Lists are updated every 4 hours.

Although there are no specific rules for domain registration, we do have the policy on dead domain records.
Your domain will become open for registration again if it is dead for:

Your domain will generally be approved within 24 hour(s). However, your domain must be alive within the last 3 hour(s) before the approval is due.

External subscriptions:
Our service fetches external subscription updates daily. List of external services: