Library for Bayesian Optimization?(using Gaussian Process)

A good library for doing bayesian optimization? I came across 'BayesOpt', but seems new and untested? At this point if there is a place where someone has written those programs, I would love to have a look at them. To be clear, I am talking optimization where underlying function is approximated by a gaussian process and acquisition functions for predicting the next point for optimality are max of 'expected probability of improvement' or ratio of mean+K*variance etc