The gist is, by "officially" releasing it now, Dylan's label can prevent bootlegging of the songs and release them more widely at a later date.
Although the European Union has extended copyright terms from 50 years to 70 years, the extension only applies to recordings that have been released during the 50 years after they were made. Sony was therefore forced to release these songs – albeit in limited form – before the end of 2012, when their half-century was up.
"This isn't a scheme to make money," a source explained to Rolling Stone. "The whole point of copyrighting [this material] is that we intend to do something with it at some point in the future. But it wasn't the right time to do it right after [Dylan] released Tempest."