EFL are Enlightenment Fundamental Libraries - the underpinnings of the Enlightenment Desktop Environment. And the author is writing on the Enlightenment websit

EFL are Enlightenment Fundamental Libraries - the underpinnings of the Enlightenment Desktop Environment. And the author is writing on the Enlightenment website: it's clearly intended for current developers/users of Enlightenment, who would probably know what EFL stands for. So it doesn't say anything about the author, who is writing for a known audience.