Free Software, DaaS Sales Model

I've been working on my "CherryPC Business Apps" and decided to make the software free and only charge for "Data Services". The apps use CouchDB/PouchDB, Bootstrap, jQuery, and a few other open source libraries. So the "Data Services" include storing data in a remote CouchDB Database, syncing the data on all the desktop computers and mobile devices connected to it, and weekly backups of all the data at an offsite storage facility. I've configured the apps so they don't need the "Data Services" to be usable, and they run offline. I think this model has some interesting benefits for both the provider and the end users. You can find it at https://cherrypc.com Any thoughts?