That's only important if the plan is to stay feature-compatible with the original going forward.
For this case, where it's used as an internal filtering engine, I expect the goal is fixing bugs that show up and occasionally adding a feature that's needed by this organization.
This case looks like pure marketing fluff rather than sound engineering tho.
>expect the goal is fixing bugs that show up and occasionally adding a feature that's needed by this organization.
Even if we assume a clean and bug free port, and no compatibility required moving forward, and a scope that doesn't involve security risks, that's already non trivial, since it's a codebase no one has context of.
Probably not 500k worth of maintainance (because wtf were they doing in the first place) but I don't buy placing the current cost at 0.