This is the GAIAST code, it is Fortran 2008+ standard compliant and is free, and an open source project. It is distributed under a multi-licensing system:
We use Ideal Adsorbed Solution Theory (IAST) to predict the loading of the gas mixture on the adsorbed phase, based only on the knowledge of the pure adsorption isotherms of the individual components.
"input", "isoterma1.dat", "isoterma2.dat", "isoterma3.dat", etc.