That is a steam restriction. Not a Ylands restriction.
Steam updated this months ago to stop people from buying the game from another region of the world where it was substantially cheaper and gifting it to a friend or another account where it was more expensive.
In the process it stopped millions of users from gifting games to friends across the shared border. Saves me money in the long run as I am no longer gifting tons of games to my friends in the US. Steam loses out with this setup.
You can have your friends login in your machine, then you make the purchase on their account with your payment info. (Remember to not save your info)
Log out and back into your account and your friend now has Ylands.
There are ways to work around some restrictions.
I have done this using teamviewer and letting my friend log into their account on my computer. So they login and not you. Meaning they didn't share their account information with you.
