Historically it was available as a purchase from Gurobi.
However the software is now defunct(*) and I no longer see it on their site. You can see how it used to look here.
You might try contacting them directly.
(*)In May 2012 last year, the Solver Foundation team wrote: The current 3.1 release of MSF will be the last release as a standalone install. We are working hard on integrating Microsoft Solver Foundation into a larger analytics framework that will help users build both prescriptive and predictive analytics. We look forward to releasing this new product for your use as soon as we are able to do so. This new product will provide a migration path for current Solver Foundation users and partners.