Lacking proper maintenance, so anything on this page likely won't work.
Hellspawn -- Hellnet daemon in Qt/C++. Supports data inserting, retrieving, message parsing and even some network connectivity. Doesn't work out of localhost, development is stopped in favour of hspawn.
Hspawn -- Hellnet daemon in Haskell. Currently supports data inserting and retrieval (optionally encrypted), tech/metatrees, manual bootstrapping and semi-automatic server discovery.