The lookahead implementation in opensmt is not yet in the master branch of the opensmt git. You can compile the lookahead version of opensmt by
$ git clone https://scm.ti-edu.ch/repogit/opensmt2.git
$ git checkout lookahead
$ mkdir build; cd build; cmake ..; make
The binary will be in ./src/bin/opensmt
Opensmt requires the gmp libary for arbirary precision mathematics, and the readline library to compile.