There are no public releases of Nidhogg yet. To download Nidhogg you will have to download the source code and compile the code yourself. To access the source code you can either use subversion or download an automatically generated tar-file.
Nidhogg uses a system called Subversion (SVN) to maintain the source code. To download the latest source code directly from the SVN server; execute the following command:
svn checkout svn://svn.code.sf.net/p/nidhogg/code/ nidhogg-code
Browsing the SVN tree:
To explore the SVN repository you can also use the web interface.
If you do not have SVN installed you can also download an autogenerated tarball: nidhogg-trunk.tar.gz