BOKU Inc. is a publicly listed company based in San Francisco. It offers a popular mobile billing option that is available for many different goods and services worldwide, including gambling. It is popular for those who have a phone but no bank account, or for those who just find mobile billing an easier and more convenient payment option. Other common uses for BOKU are to pay for online services like music streaming, virtual goods, social networks and gaming.
You can read more on their website here: www.boku.com