You say it is forbidden to climb, but then talk about a summit register? This is very confusing.
I'm serious. If you ask for permit to climb, they won't let you.
But the owner of the Banco de Chile is a famous chilean climber (with some 8000 peaks done btw) and it was his idea the project.
If you go, don't ask for the permit, just climb the volcano.
I know it is confusing but it is true.