Warning: this COPR repo is experimental (I'm learning how to build COPR package as we speak) and does not contain actual packages, please refer to cottsay/gringo or jonludlam/opam insteand -- but they don't have Fedora 25 packages.
This is a companion discussion topic for the original entry at https://copr.fedorainfracloud.org/coprs/wangd/opam/