title: Free solver for MINLP
body: <p>I am trying to solve a MINLP and I use Pyomo and Spyder. I am looking for a free global solver for many variables and constraints and it should be matched with Pyomo.
  Baron is a global solver but it needs license for more than 10 variables and 10 constraints. I used Knitro solver but it is a local solver and it was stuck in local optimum.
  Which solver do you recommend?</p>