docbook2mdoc — DocBook to mdoc converter
The docbook2mdoc utility is a converter from DocBook version 4.x and 5.x XML to mdoc. Unlike most DocBook utilities, it’s a standalone ISC-licensed ISO C utility with no external dependencies that should compile on any modern UNIX system.
docbook2mdoc is no longer experimental, but many features are likely to still be missing, and the rendering of many elements is not ideal yet. However, it can already be used for production purposes and was tested on parts of the OpenGL and X.Org DocBook corpuses.