HFSS For LInux
It's not free, but it runs on any linux distro. They only let you install or run it on RedHat or SUSE though, but there is a way around. You have to edit all the config files and comment out all the lines that check if you are running SUSE or RedHat.
I have no idea why they do the checks, I installed it on Debian and it runs.
I cannot post the config files, they are copywritten, but its easy to figure out if you know basic programming syntax.
Added after 53 seconds:
Oh yeah, you download it from ansoft directly, if you have a license, they will provide you the information.