The best open source alternative to Quip is Joplin, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Quip and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Quip are LibreOffice - Writer (Free, Open Source), Standard Notes (Freemium, Open Source), CherryTree (Free, Open Source) and ONLYOFFICE (Freemium, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Etherpad is a highly customizable Open Source online editor providing collaborative editing in really real-time. Collaborating in really real-time No more sending your stuff back and forth via email, just set up a pad, share the link and start collaborating!