GCompris - Educational Game for Children 2 to 10 years old.
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Tux Paint - Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6).
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
childsplay - Childsplay is a collection of educational activities for young children and runs on Windows, OSX, and Linux. Childsplay can be used at home, kindergartens and pre-schools.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface