pycess
Process machine for creating web applications, based on Django/Python
... allowing arbitrary complex processes to be realized, pycess is less ambitious with regard to sophisticated desktop-like user interfaces.
Django serves as the application framework, based on Python, which runs on most common OSes like Linux, BSDs and Windows.
Databases need to provide DB functions or recursion, like PostgreSQL, DB2, MS-SQL, Oracle (not MySQL).
Read the Wiki page for more.