Apache is a free and open-source cross-platform web server software.
Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.