We have just finalised Namecoin Core 0.18.0: https://github.com/namecoin/namecoin-core/releases/tag/nc0.18.0

This is based on the recently-released Bitcoin Core 0.18.0 and thus includes a lot of new features (e.g. improved multi-wallet support) in addition to some Namecoin-specific changes.

Important:  This release schedules a softfork at mainnet height 475,000 (expected to be mined in about half a year from now), which will finally activate BIP16 (P2SH) and Segwit.  Everyone should update as soon as possible.