Say you started as SaaS service with freemium business model such 37Signals - Basecamp or Dropbox etc..Is there an OSS license that says that you can use the source code etc.. but you cant release a SaaS based on it, esssentially released in good faith with non-compete expectations. e.g. if 37Signals released the source for highrise, basecamp etc.. someone could start 37signals4lesss.com (albeit once they built the same bit of provisioning logic) and damage the core business model. 
Is there an OSS license that works for this:
open source