Hspice is one of the industrial standard circuit simulator, so it's not free obviously. Hspice still hold on direct netlist text file manipulation, no schematic gui (anyway, there are some 3rd party softwares offer it), that feel uncomfortable to many people. But if you are familiar with it enough, you will find its advantage.
Actually and Obviously Hspice is not a freeware tools. and we should also agree that it's GOLDEN tools now in AMS design, although Spectra and other simulator are also very good. But if you just want to self study, I think you can find HSpice in network; IF you do bussiness, please get it from its provider. Lucky to you!