Since the URL does not exist, I believe this is the successor of what we have in portage: https://github.com/cucumber/cucumber-ruby
Yes, that is correct. Unfortunately, due to new dependencies, we cannot add this version without dropping ruby22 support at the moment. cucumber depends on parts of Rails indirectly, and several components are not compatible with ruby22 yet. We fixed i18n by incorporating an upstream pull request, but at least thor is still an issue due to its testing dependencies. This is fixed in upstream thor, so hopefully there will be a new release soon.
dev-util/cucumber-2.4.0-r1 has been in the tree for some time (and 2.4.0 before that) but I missed closing this bug at the time.