From here you can download MIGRATE. The program exists in two major versions. Version 3 will not develop further, it can evaluate population models that include populaton sizes and immigration rates. Version 4.x included estimation of divergence times. I have added addtional population models to it, eventually they will become visible but will need more testing. At the moment, if you want to download the source distribution pick version 5.x because it contains all the models from version 4.