You're right it should have an introduction where it does mention what it is. This project might be in need of some love.

Open Genera is the Genera OS[1][2] which used to be run on Symbolics Machine. Open Genera[3] is the Genera OS running in a virtual machine.

[1] http://c2.com/cgi/wiki?GeneraOs

[2] http://www.textfiles.com/bitsavers/pdf/symbolics/ (mentioned on the wiki)

[3] http://c2.com/cgi/wiki?OpenGenera