Apache Friends Support Forum

Hi Brothers,
I am PHP programmer. I develop applications like school management, Point of Sales (POS) using PHP and MYSQL for my clients.

Now my question is that:

Is MYSQL free which is in XAMPP? If I use XAMPP in my client's computer to configure Apache, PHP & MYSQL environment.
Have I to pay for MYSQL license? If I use XAMPP.

Please give me documentation (if any).

Thanks

Current XAMPP versions don't implement Mysql, but Mariadb.
Read more about Mariadb licenses here:
https://mariadb.com/kb/en/library/licensing-faq/