Assign New User a Default level

See this post for information: https://www.paidmembershipspro.com/2015/03/give-users-a-default-membership-level-at-registration/

I’m also trying to achieve similar system. But, the solution is only for paying members.
I support the ‘premium help/fix’ system but I’m not just ready yet to subscribe for your membership plan. So, is it possible to buy only this fix for a small fee?
Actually, I’m using Profile builder plugin to get registrations and I want to assign all new users automatically to a free PMPro level when they register using Profile builder front-end registration form.

And really thanks for this great plugin.
Nitya