The best free alternative to collabedit is Plunker, which is both free and Open Source. If that doesn't suit you, our users have ranked five alternatives to collabedit and four of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to collabedit are Squad (Freemium), Rustpad (Free, Open Source) and evocode (Free).
Squad is a collaborative web-based code editor with one goal: to make it easy to open, edit, and share code in real time. Our powerful, secure tools include syntax highlighting, cloud hosting, a searchable chat log, and multiple syntaxes.