I met with @daantimmer today who has built a ground-up implementation of Cucumber for C++ based on the official Gherkin parser.
https://github.com/philips-software/amp-cucumber-cpp-runner
He has released it under Philips' GitHub org to streamline the internal bureaucracy around contributing to open source, but it is released under an MIT license and his goal is simply to give the community a full Cucumber runner in C++. He and his team are using it in some significant projects at work.
He has implemented a tag expressions and cucumber expressions parser, and the tool supports custom parameter types. He has a goal to refactor it to use the Google Test Runner, but it currently implements its own test runner.
It does not currently support a wire protocol server.
I would like to facilitate some dialogue between the current maintainers of this package and Daan to see if we can work out a way forward that makes the best of both implementations and combines our efforts.