Apache is a free and open-source cross-platform web server software.
Braintree, a division of PayPal, specializes in mobile and web payment systems for ecommerce companies. Braintree provides clients with a merchant account and a payment gateway.
Paysafe is a payment platform that enables businesses and consumers to connect and transact by payment processing, digital wallet, and online cash solutions.
Stripe offers online payment processing for internet businesses as well as fraud prevention, invoicing and subscription management.