Worth noting: A year ago, Digital River announced in an SEC filing that it had come to an agreement with Microsoft to "build, host and manage the Microsoft Store, an e-commerce store that supports the sale and fulfillment of Microsoft and third party software as well as consumer electronics products, to customers throughout the world." It's possible that downloads from the Microsoft Store may, in fact, be coming from Digital River servers. Same applies to retail discs, the process of ordering, shipping, nominal fee.
The persons these Digital River downloads would be most suitable for, even if they didn't purchase through the Student upgrade program are persons with OEM preloads who might have lost their recovery partitions or media and can't bother with the process of obtaining recovery media.
If you bought Windows 7 retail, then it will already be accompanied with install media, if you bought it from the Microsoft Store for instance, you have the option of downloading it anytime you want or have discs shipped to you or if its a box license, you will have two physical discs. The way I see it, the license takes precedence over the medium. Since it is being download directly from Digital River servers, as long as you own a genuine license, which you probably should have already, then you are free to download it. Microsoft MVP and Answers forum moderator Andre de Costa put it this way: Over the years, many Windows experts - including MVPs posting on the Microsoft Answers forum - pointed customers to the Digital River links that contained real, direct-from-Microsoft copies of the software. Most Windows customers came to know about Digital River through various Windows student/academic discount offers: Digital River apparently ran the student discount programs and provided "genuine" Windows bits for download. It isn't clear if there's a technical problem or if Microsoft's contract with Digital River has lapsed. But in the past few days, the links for Windows 7 SP1 versions at Digital River stopped working. That changed several years ago, when Microsoft contracted with outsourcing company Digital River to provide download services for Windows bits. For Windows customers without immediate access to MSDN (or the defunct TechNet), acquiring genuine Windows ISOs has been a frustrating and ridiculously complex experience: Microsoft tells you to ask your hardware manufacturer for a Windows ISO the hardware manufacturer either ignores the request or sends you a crap-filled recovery DVD, frequently charging you for the inconvenience.