This reactor prototype has gotten private investment, because it is both comparatively affordable (hundreds of millions instead of tens of billions of dollars) and it will likely be profitable to license the technology to commercial plant operators. It is unlikely that commercial reactors would require public funding.
Decommissioning costs should be negligible because the reactors won't generate radioactive fission byproducts. The reactor chamber is designed for a 10 year lifespan and easy replacement. The old chamber is slightly radioactive (due to neutron bombardment) for a few decades, which is much less of a problem than the highly radioactive waste from fission plants that has to be stored for thousands of years.