At a time when many independent booksellers both here and abroad are beginning to gain traction selling Kobo e-books, other retailers are eyeing the secondary market for e-books and other digital content. Boston-based ReDigi, which opened a used digital music storefront in late 2011, may have gotten there first, but megaretailer Amazon isn’t far behind. Last month Amazon received a patent to create a digital marketplace for used content, including used e-books and audio downloads, much like the one it already provides for sellers of used print books and CDs.

There’s still one obstacle for ReDigi to overcome, at least in the U.S: a lawsuit that Capitol Records filed in January 2012 claiming that ReDigi is violating copyright. Capitol called ReDigi “a clearinghouse for copyright infringement,” rejecting the idea that it is the digital equivalent of a used CD store. That doesn’t worry founder, president, and CEO John Ossenmacher, who is moving forward with plans for expansion both in the U.S. and in Europe. The only concession that the technology entrepreneur has made, at the advice of the company’s attorney, is to keep the site in beta until the suit is settled. Ossenmacher said that because the case is so technical, ReDigi elected for trial by judge, but he never realized that it could take three months and counting for Judge Richard J. Sullivan of U.S. District Court in the Southern District of New York to reach a decision.

One of the reasons that Ossenmacher, who was recently appointed to the Congressional Internet Caucus’s Advisory Committee, is optimistic he will prevail is that ReDigi uses a so-called “verification engine” to determine whether a given song, or soon an e-book, has been legally downloaded and can be resold. And it provides an “atomic transaction” that transfers content without copying it. “With ReDigi’s method,” states Ossenmacher, “only the ‘original’ good is instantaneously/atomically transferred from seller to buyer, without any copies. ReDigi then assists the seller with an antivirus-like software application that monitors the seller’s computer and synced devices to ensure that any personal-use copies of the sold good are removed.” By contrast, the patent obtained by Amazon appears to rely on a “copy-and-delete” mechanism, which is at the heart of the Capitol suit (Amazon didn’t respond to PW’s queries).

In addition, what separates ReDigi not just from Amazon but from sellers of used physical books and CDs is that it pays artists and other copyright holders (and soon authors and publishers) when it sells pre-owned digital media. And ReDigi is interested in more than used content. It currently sells new music as an iTunes affiliate—and it will sell new e-books in addition to used Kindle, Nook, and Kobo titles. ReDigi is format-agnostic. Although Ossenmacher declined to release any statistics, he did note that ReDigi’s users spend the majority of their sales earnings—users get ReDigi credits for selling used content—on new rather than used music.

The prospect for a ReDigi used and new e-book marketplace looks rosier on the other side of the pond, where the company has already received hundreds of thousands of positive responses to the announcement that it will open a store in the European Union. The company will start by establishing a European headquarters, most likely in the U.K., which will be followed by the opening of a marketplace within four months that will include music, e-books, and used software. Two legal actions should help pave the way. In July, the Court of Justice of the European Union in Luxembourg ruled against software developer and distributer Oracle, finding, in effect, that selling software for a fee and calling it a license still allows it to be resold. The second case involves the Federation of German Consumer Organizations (VZVB), which sued computer game distributor Valve in the District Court of Berlin in January for prohibiting users from reselling its game Steam. Although not settled, Carola Elbrecht, project manager for consumer rights in the digital world at the VZVB, argued that “Steam users own the games they purchase and should be able to resell them when they want to, just like owners of traditional card or board games can,” according to PC Advisor.

While ReDigi looks abroad for growth, it continues to enlarge its U.S. presence. In recent months it has moved its U.S. headquarters across the Charles River from Tech Square in Cambridge, Mass., to the Prudential Center in Boston. It currently has between 20 and 25 people on staff in Boston, California, and New York City. Next on its docket after e-books and software are digital games—just in time for the 2013 holiday season.