@jebba I believe hat site is expired and not up-to-date anymore, meaning its currently not in use.
The new system is based on a contract on Ethereum. As far as I understand the subdomains should be xyz.rad.eth where xyz is the name you’d register. For now you can interact with the raw-contract (e.g. via Etherscan). Go to the Contract → Write → register function.
This is correct, except names are under radicle.eth instead of rad.eth.
The radicle ens registry registry uses a commit/reveal scheme to help prevent front running.
If you want to register a name you must first submit a commitment to that name by calling commit(commitment) where commitment is keccack256(abi.encodePacked(name, owner, salt)). salt should be a random number. Making a commitment costs registrationFeeRad RAD (currently 10).
Once the commitment has been successfully made, you must wait minCommitmentAge blocks (currently 10) before you can call register(name, owner, salt).
There is some deeper technical analysis regarding the registrar in the audit report: Radicle Audit Report:.