According to the Oxford English Dictionary, a lingua franca is "a language that is adopted as a common language between speakers whose native languages are different."
In business or educational environments where speakers from different countries need to communicate, they usually use English as a common language that everyone will understand.
ELF emphasizes the international use of English, not the specific culture, usage or accent of American, British, Australian or other types of English. Communication and intelligibility are more important in ELF than trying to use English like a native speaker.