If nobody owns the trademark then they're free to use it.

The person who wrote this post tried to register the trademark to prevent them from using it. If the trademark is determined to be abandoned and generic then they cannot stop Ruby Central from using it.

but ruby central using the trademark is not the problem. as long as everyone else can use it too. but ruby central wants to prevent everyone else to use it, and that's the problem.

if the trademark is determined to be generic, then ruby central can not prevent anyone from using it.

the goal is not to stop ruby central from using the trademark. the goal is to stop them from claiming ownership.

I think the point is to prevent Ruby Central from owning it, not using it