GIS server and client?

[Bob Collins]

I am unfortunately running ESRI's ArcIMS GIS server on M$ 2000 server
and would like to move it to FreeBSD. So, the question is; are there any
known GIS servers that run on FBSD as well as clients?

I am not afraid of hard work and troubles installing, but sure would
like to do this. I also know ESRI's ArcIMS runs on Red Hat, but I would
rather not do that if possible. I want to stick with FreeBSD.

Any and all suggestions, as related to the questions ;-) are
appreciated. Thanks

-- 
Bob