An admirably concise definition by Trebor Scholz on loc 432 of Uberworked and Underpaid:
This term can be briefly described as follows:
First, it is about cloning the technological heart of Uber, Task Rabbit, Airbnb, or UpWork. Platform cooperativism creatively embraces, adapts, or reshapes technologies of the sharing economy, putting them to work with different ownership models. It is in this sense that platform cooperativism is about structural change, a transformation of ownership models.
Second, platform cooperativism is about solidarity, sorely missing in an economy driven by a distributed and mostly anonymous workforce: the interns, freelancers, temps, project-based workers, and independent contractors. Platforms can be owned and operated by inventive unions, cities, and various other forms of cooperatives such as worker-owned, produser-owned (producer-user –produser), multi-stakeholder, co-ops.
Third, platform cooperativism is built on reframing concepts like innovation and efficiency with an eye toward benefiting all, not just sucking up profits for the few. I propose ten principles of platform cooperativism that are sensitive to the critical problems facing the digital economy right now. Platform capitalism is amazingly ineffective in watching out for people.