I am working on SAAS, and I want to open source the codebase. But I'd like to avoid a big commercial entity to run my software as a competitive service. What i

I am working on SAAS, and I want to open source the codebase. But I'd like to avoid a big commercial entity to run my software as a competitive service. What is the best license to use for this use case? I want to allow as many uses of my code as possible, like on premise deployment, schools, ... But with the exception of using it commercially to run the same service as me.