Hamstersoft Ebook Converter rips off calibre

A hot new ebook converter popped up just over a month ago, and it turns out there's a problem with it. Hamstersoft was hailed by all the tech blogs as this great new way to covert ebooks from one format to another. It had a simple interface, foolproof operation, and a lot of enthusiastic users. Unfortunately, the Hamstersoft Ebook Converter is also a pretty egregious example of copyright infringement. According to John Schember (a calibre contributor) the Hamstersoft Ebook Converter uses large chunks of code from the calibre ebook library app and doesn't comply with certain GPL (GNU General Public License) conditions. Update: Hamstersoft has taken down the ebook converter and promised to comply with the GPL. let's see what happens.

You can find the full details over on John Schember's blog. It's technically complicated and quite long so I'll just cover the basics here.

John is one of the contributors to calibre (he's also now the maintainer for Sigil, the epub editor). Like most open source developers, John contributed code under a GPL license and kept the copyright.

I wanted to make that point clear because it's important to note that when Hamstersoft ripped off calibre, they didn't just steal code from a single developer. They pirated code written by a dozen or more people, all of whom have good reason to now sue Hamstersoft.

John kept the copyright on his code, and he contributed that code under a GPL v3 license. Pretty much anybody can use his contributions - just so long as  they comply with certain conditions. Hamstersoft neglected to follow a key condition of the GPL. Specifically, they are required to release the source code for Hamstersoft Ebook Converter. Thus, they don't have any license to use the code.

John contacted Hamstersoft shortly after the Hamstersoft Ebook Converter launched (when he noticed that it used code from calibre). Hamstersoft apologized for the error, and they promised to comply with the license requirements. They didn't.

It's been a month since John contacted Hamstersoft, and that's all the time he's willing to give them to correct their error. Right now he's going around to all the hosting sites and filing DMCA notices. It's a work in progress.

About Nate Hoffelder (11463 Articles)
Nate Hoffelder is the founder and editor of The Digital Reader: "I've been into reading ebooks since forever, but I only got my first ereader in July 2007. Everything quickly spiraled out of control from there. Before I started this blog in January 2010 I covered ebooks, ebook readers, and digital publishing for about 2 years as a part of MobileRead Forums. It's a great community, and being a member is a joy. But I thought I could make something out of how I covered the news for MobileRead, so I started this blog."

8 Comments on Hamstersoft Ebook Converter rips off calibre

  1. Timothy Wilhoit // 14 August, 2011 at 1:11 pm // Reply

    HamsterSoft is a Russian company…that complicates matters a bit.

    • That explains a lot. Having another country rip off your code makes it very hard to battle because of the laws, borders and governments involved. And they know it.

      If Hamstersoft had any honor, they would do the right thing and properly address John’s issue. Alas, it appears there is no honor to be found at Hamstersoft.

  2. you jumped the gun // 14 August, 2011 at 3:23 pm // Reply

    they do offer the source, at the bottom of their page at


    they have a link to the source code and according to the server it was made available on july 21st

    Content-Type: application/zip
    Content-Length: 64444164
    Last-Modified: Thu, 21 Jul 2011 07:53:35 GMT

    • John said that it’s not a complete set of the code.

      • you jumped the gun // 14 August, 2011 at 3:54 pm // Reply

        i see now, my bad…
        i looked closely through that zip file and the main UI dll appears indeed just as a binary-only blob without its source… sneaky…

      • The night it came out (or the night after), Kovid Goyal was on a few Mobileread forum threads saying what HamsterSoft did was a rip-off of Calibre, so I decided to not even mention them.

        But Calibre ought to put together something as easy to use as that software is said to be.

        • Well, I forgot — that would be illegal 🙂

          The current tools by a 3rd party person certainly makes it easy enough and Calibre is just ‘used’ in that case.

  3. Factual correction: They have complete permission to use the software, what they lack is permission to distribute the software.

2 Trackbacks & Pingbacks

  1. The Hamstersoft & calibre GPL issues have been resolved - The Digital Reader
  2. Calibre updated - The Digital Reader

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