An interview with Kovid Goyal of calibre

Growing up, Kovid Goyal planned to be a physicist working on quantum computers. However, while studying at the California Institute of Technology (CalTech), he began developing calibre, an ebook manager for GNU/Linux, OS X, and Windows. The project quickly grew, developing its own ecosystem of sub-projects, extensive documentation, and self-funding. Today, calibre is a full-time vocation for Goyal, as well as a partial source of income for other project members.

Goyal recalled:

A GNU/Linux user from the age of fourteen, first on Red Hat and later on Gentoo, Goyal worked his way through grad school by administering the particle theory group's computers at CalTech. An avid reader, he was dismayed to learn that the SONY PRS-500, the first reader to use e-ink technology, did not support his operating system of choice. In response, he wrote the first version of calibre, which he originally named libprs500.

From this beginning, the project grew as Goyal discovered other missing tools for ebooks. The conversion features were added because Goyal wanted to convert ebooks for his reader. Similarly, management collection tools and a graphical interface were created as his ebook collection grew, and the news downloading tools when he could no longer get Newsweek delivered to his door. Other features were added by contributors such as John Schember who created the "Get Books" feature in calibre, which provides a comprehensive list of ebook publishers as well as a comparison shopper. Recently, Schember also became maintainer for Sigil, an ebook editor in early release.

In 2008, the project was renamed by Goyal's wife, Krittika Goyal. On the project's history page, Kovid Goyal explains that "the 'libre' in 'calibre' stands for freedom, indicating that calibre is a free and open source product, modifiable by all. Nonetheless, 'calibre' should be pronounced as 'cali-ber,' not 'ca-libre'." Krittika Goyal is also responsible for Open Books, a portal site for ebooks unencumbered by Digital Rights Management (DRM). Kovid Goyal commented:

Currently, the site lists several thousand titles by publishers ranging from small presses to Baen Books, a major science-fiction publisher.

Today, calibre has evolved into an active project, with new releases every Friday. Growth of the project remains steady, with many of the revisions consisting of drivers for readers, new magazine downloads, or interface refinements. However major new features are still being developed as well. Recently, for instance, calibre added a plug-in structure, whose success can be seen from the "Plugins" menu under "Preferences". There is even an unofficial plugin for removing DRM, although Goyal stressed that:

Since calibre collects statistics based on unique IDs and IP addresses whenever an installation starts, Goyal can track current usage in some detail. He reports that calibre has about four million users who have used the application at least once, and is growing at a rate of three hundred thousand users every month. About eighty percent of users are on Windows, seventeen percent on OS X, and three percent on GNU/Linux. By any standard, calibre is a free software success story, an all-in-one application that is to ebooks what Amarok is to music players, or digiKam is to images.

Keys to success

The most obvious cause of calibre's success is its comprehensive feature set. However, another part of the project's success lies in two areas often neglected by other projects: documentation and fund-raising.

Help is available on the project site in forms ranging from an FAQ and an introductory video to step-by-step guides on conversion to and from various ebook formats and a complete user manual. This thoroughness "is a deliberate policy", according to Goyal:

Yet, as important as documentation is, probably the single most significant feature of the calibre project's culture is its active fund-raising. Unlike most free software applications, calibre includes a button for donations, as well as a discreet donation button on the project's home page. "Donations are essential to my being able to work full-time on calibre," Goyal said. "I am continually amazed by the generosity of all of calibre's donors, many of whom have continued to donate repeatedly over the years."

However, donations are not the only source of calibre's funding. Hosting is paid for from a single sidebar ad on calibre websites. Goyal and some of the other most active project members also do some calibre-related consulting. Although confidentiality prevents him from being specific about this work, he explained that, "In general, it involves consultation for companies that are trying to enter the ebook market. Some [of it] involves customizing calibre for a particular organization/use case."

Yet another source of income for all project members is the Get Books store browser and comparison shopper feature. Most of the links on Get Books are part of publishers' affiliate programs, and revenue from such programs are divided, with seventy percent going to the developer who maintains a particular link and thirty percent to Goyal. "The two most active developers (by commits) John Schember and Charles Haley, get most of the income from Get Books," Goyal said.

To some, this emphasis on funding might seem opportunistic, but Goyal remains unapologetic:

Moreover, it is hard to argue with success. If calibre remained entirely a volunteer project, then it would undoubtedly be less advanced than it is. Unsurprisingly, Goyal anticipates other possible income sources, such as personal calibre clouds, with hosted services "for those who would rather not deal with maintaining their own cloud."

Future possibilities

Currently at version 0.8.15, calibre is still very much a work in progress. Although calibre already far exceeds the features of any of the software shipped with ebook readers, tentative future plans include a number of major additions. They include improved conversion to PDF and MS Word formats, a reworked ebook viewer with the ability to read HTML 5, and support for annotations across multiple operating systems and readers. "But I must emphasize that things happen in calibre land very serendipitously", Goyal said. "People scratch their itches and calibre grows new capabilities. So please do not regard this as a list of promises." His overall goal is clear:

Meanwhile, the continued success of calibre seems assured. Not only is it a feature-rich application with no major rivals, but its funding efforts allow Goyal and other developers to concentrate on their work while keeping their autonomy.