@Ron - Plugin as a service is allowed.
I asked Matt this earlier
Plugin/theme that integrates with a must pay for service

There are plenty of plugins that tie into third-party services, for example Google Adsense, and some of them have no free versions. That's totally fine as long as the plugin is totally GPL.

I'm not sure how that would work with a theme, that seems way more user-hostile. It could still be legal under the GPL, but just like putting artwork included with a theme under a restrictive that's probably not something we'd want to promote on WordPress.org.