Proprietary software on the other hand tends to use a different business model, where a customer of the proprietary application pays a fee for a license to legally access and use it. This license may grant the customer the ability to configure some or no parts of the software themselves. Often some level of support is included in the purchase of proprietary software, but additional support services (especially for enterprise applications) are usually available for an additional fee. Some proprietary software vendors will also customize software for a fee.
Practically the de facto reader for ebooks these days, the Kindle brand is more than just hardware—it extends to these apps and programs for reading ebooks (which you have to buy from Amazon, of course). Start the book on any device, continue it elsewhere—the Kindle WhisperSync feature knows where you stopped reading. X-Ray gives you insight into the book; GoodReads integration gives you a social aspect. The new PageFlip lets you keep your page while scouring the rest of the book.