How to install LP_solve solver on Yosemite?
The easiest way is doing it using homebrew. You just need to type the following couple of commands in a terminal window:

brew tap brewsci/science
brew install lp_solve


If you don't have homebrew installed, just type the following to install before the previous commands:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"