Is the hourgator.com website free to use?

Yes, it is totally free of charge.
As opposed to many websites there are no upgrading schemes, no golden memberships,
no charges for messages when someone wants to respond or contact a website user.
No-one from the hourgator.com will ever contact you in any way to ask about your credit card information or money.

Why register?

If you want to post you have to register.
You register using your email address which is unique to every person, yourself included.
This is the only, unique identifying feature you have from the hourgator.com database's point of view.
While the database does not know your first or last name it knows that the person who has your email address posted a particular post and is able to find and retrieve its details when someone clicks on it.
Without registering the database would not know whose posts belong to whom.