Hey everyone, sorry for taking so long to update this, it will be updated shortly and contain discrete capability as well as multi-objective optimization built in and more flexible constraints (linear or nonlinear). If you wish to do multi-objective opt "lite" right now you can, just write your cost function so it has a weighted sum of your objectives as the output, a standard way to do it. More complex methods will be added with the update.
I think I found a crucial bug: in my program I write down the test parameters if they fit better than in the iterations before. In my test PSO stopped after fulfilling a break condition and gave me a final parameter set, which fitted less than an intermediate result I wrote down before.