Multi-wavelength secondary-eclipse and transit depths probe the thermochemical properties of exoplanet atmospheres. In recent years, several research groups have developed retrieval codes to analyze the existing Spitzer, HST, and ground-based data and study the prospects of future facilities. However, the scientific community has limited access to these packages. Here we present the open-source Bayesian Atmospheric Radiative Transfer (BART) code (github.com/exosports/BART). We will discuss the key aspects of the BART components: the Thermochemical Equilibrium Abundances code, TEA (github.com/dzesmin/TEA), to calculate species mixing ratios by minimizing the system's Gibbs free energy; the one-dimensional line-by-line radiative-transfer code, Transit (github.com/exosports/transit), to calculate transmission or emission spectra; and the statistical package Multi-core Markov-chain Monte Carlo, MC3 (github.com/pcubillos/MCcubed), to estimate best-fitting parameters and posterior sampling using Bayesian principles. We apply the BART retrieval code to the HAT-P-11b transmission data to constrain the planet's molecular composition. We will compare our results against those of Fraine et al. (2014).