WikkaWiki : WikkaWiki is a flexible, standards-compliant and lightweight wiki engine written in PHP, which uses MySQL to store pages.
PredictionIO : PredictionIO is an open source machine learning server for software developers to create predictive features, such as personalization, recommendation ...
Budibase : Budibase is an open-source low-code platform for creating internal apps in minutes. Supports PostgreSQL, MySQL, MSSQL, MongoDB, Rest API, Docker, K8s
GetSimple CMS : GetSimple is an XML based, stand-a-alone, fully independant and lite Content Management System.
Wavacity : A free and open source audio editor for the web derived from Audacity
CryptoZombies is a free, open source, interactive code school that teaches you to build games on Ethereum. The course is designed for beginners to Solidity and starts off with the absolute basics.