To look up Namecoin names (e.g. in conjunction with ncdns), you need a Namecoin name lookup client.
Your options are:
- Namecoin Core
Namecoin Core is the port of Bitcoin Core to Namecoin. Namecoin Core is a fully validating node, is reproducibly built, and supports Tor. You can download Namecoin Core at the Downloads page.
ConsensusJ-Namecoin is a lightweight SPV name lookup client, based on ConsensusJ, libdohj, and BitcoinJ (also used in the Schildbach Android Bitcoin Wallet). ConsensusJ-Namecoin is written in a memory-safe language (Java), which is more secure than Namecoin Core, but it isn’t a fully validating node, which is less secure than Namecoin Core. ConsensusJ-Namecoin is not reproducibly built and does not support Tor. ConsensusJ-Namecoin documentation is here.
Electrum-NMC is the port of Electrum to Namecoin. Electrum-NMC is written in a memory-safe language (Python), which is more secure than Namecoin Core, but it doesn’t verify completeness of blocks, which is less secure than Namecoin Core and ConsensusJ-Namecoin. Electrum-NMC is not reproducibly built. Electrum-NMC supports Tor.
After you’ve installed a Namecoin name lookup client, if your goal is to access
.bit domain names, your next step will be installing ncdns.