[Freeswitch-users] Looking for libesl, headers, etc.

I built a Debian 9 based FreeSwitch+FusionPBX from packages. I now want to create a simple C++ program talking to FS using the ESL. I can't find libesl on the system, nor header files. Is this available as a separate download package? Do I have to DL the whole FS source, compile, and pull that out?