Apache is a free and open-source cross-platform web server software.
Leaflet is the open-source JavaScript library for mobile-friendly interactive maps.
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.
Piwigo is an open-source photo management software designed for creating and managing online photo galleries.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.