Never use VPN even if it doesn't goes against their terms of service because most people often face issues like account got frozen due to multiple accounts like with the same IP which always occurs while you are using VPN.
This is the risk when you use VPN, there's chances that same people are also doing the same and with that the site system will detect that same
person are also using multiple accounts, better to play if you are really well knowledgeable with each rules inside the terms of the site.
Yeah better to play by the book, casino won't be too interested for who you are or where you at to dive and research about your IP so you don't to worry about them seeing your IP, that's like your log in a physical casino. There are casino who lets you use of VPN, but they are reminding of what the risks you can face in the future if you do it, and there are some casino (mostly) that does prohibit it to avoid any legal concerns.
There are some ways to buy dedicated IP for you so you can avoid most of the issues but still remember you are in the risk.
Risk can be lessen but there's still possibilities that problem may take place by using VPNs.
Thinking about it, it is very unusual for a two person to do the same thing on the internet with the same IP add they got from free applications, but it is not impossible. Prevention is better than cure!