The risk involves a company taking a product based on open source code, significantly modifying it, and using it as the foundation for selling a service over the Web. Technically, SaaS doesn't distribute code to end users, so the provider isn't required to contribute code changes to the community at large, the way Red Hat must when it resells its version of Linux.
There's a debate brewing over what to do if companies offer open source code in a software-as-a service model, then duck their obligation to contribute changes back to the community.
