Many popular Linux and BSD distributions provide an
oidentd package that can
be installed with the package manager.
On distributions that package the latest version of oidentd, this is normally
the recommended approach.
Beware that some distributions ship severely outdated versions.
Releases can be downloaded from files.janikrabe.com.
For oidentd, these are source releases (not compiled executables).
INSTALL file for instructions on how to compile and install oidentd.
The source code can be found on GitHub. This is useful if you want to
contribute to the project, or if you want to run the latest (unreleased) code.
HACKING file for information on how to work with the source code.