So, I'm trying to understand what's going on with netcat. If anybody can enlighten me, I'd appreciate it. Here's what I've found so far:

It looks like rpms/nc was retired due to being orphaned for too long. It looks like the same thing (almost) happened to rpms/nc6.

I think netcat is too important a tool to leave out of Fedora, and I'm willing to maintain it. I took ownership of nc6, because it was a dependency of hadoop. However, it looks like it was an unnecessary Requires that could just be removed.

I checked upstream and nc6 looks like it was discontinued because nc now supports IPv6 (according to nc6 docs). I haven't yet been able to confirm whether the command lines are compatible, though, and Fedora packages/users could simply switch over to using nc if they were previously using nc6.