A published object is declared in a header file. Every source code file that includes this header file can then access this published object.
A published object is declared with the MAXON_DECLARATION attribute. Only instances of Maxon API data types can be published this way. A custom class has to be registered as a data type using MAXON_DATATYPE and MAXON_DATATYPE_REGISTER (see MAXON Data Type). Implementations of interfaces are a data type so they can be shared as a published object.