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Really real-time collaborative document editing
Mattermost is an open source, self-hosted Slack-alternative
AlloyUI is a framework built on top of YUI3 (JavaScript) that uses Bootstrap (HTML/CSS) to provide a simple API for building high scalable applications.
ONLYOFFICE<br>Online Document Editor<br>Online Spreadsheet Editor<br>Online Presentation Editor<br>Collaborative editing and commenting<br>File sharing<br>Document versions<br>Document embedding<br>Integration with Google Drive, Box, Dropbox, OneDrive<br>Document management<br>Customizable CRM<br>Web-to-lead form<br>Invoicing<br>Gantt Chart<br>Milestones<br>Task dependencies and subtasks<br>Time tracking<br>Automated reports<br>Access rights<br>Blogs, forums, polls<br>Calendar<br>Email Aggregator<br>People module (employee database)<br>Instant Messanger
sabre/dav is the most popular WebDAV framework for PHP. Use it to create WebDAV, CalDAV and CardDAV servers.