Fat-free forum software.
Laravel Software Install Script Template - Most especially awesome for Open Source Projects
Zenbership Membership Software: Achieve Membership Nirvana
NEM Blockchain NIS API Wrapper and Software Development Kit for PHP
The once to be board software for Ylilauta. Might not always be open source.
Backend library for SlickBoard - An open source forum software.
A Wix App, RSS Feed, demonstrating how to build a production ready app. Client & Server from scratch using PHP server & Wix client side libraries.
Luna is an easy and beautiful solution to build your own board.