UCL has released three open source codes for chemical modelling: UCLCHEM, UCL-PDR, and 3D-PDR. Each apply in different environments and can be found on our github page along with manuals and publication lists.
UCLCHEM is a time and depth dependent gas-grain chemical model that can be used to estimate the fractional abundances (with respect to hydrogen) of gas and surface species in every environment where molecules are present. The model includes both gas phase and ice surface reactions.
Fundamental to UCLCHEM is the assumption that UV radiation can largely be neglected. Where the UV field is strong, UCL-PDR becomes the more appropriate code. In this code, the chemistry has been simplified to allow for proper treatment of UV and X-ray radiation. Taking this further, 3D-PDR vastly simplifies the chemistry by assuming chemical equilibrium in order to allow the user to run a fully 3D model with radiative transfer.