Section 10.2. Copyright in Code

10.2. Copyright in Code

Copyright protects original expression in code, as it protects any other "original works of authorship fixed in any tangible medium of expression." Some developers use that protection to enforce the openness of their code, as with the GNU General Public License (GPL); others use it to reinforce a proprietary distribution model. But while copyright protects code's creative expression, it does not protect the functions, methods, or procedures that expression implements. Thus, even for closed code, a programmer remains free to study interfaces and functionality, free to interoperate or replace that code with his own.

Situated as it is in an environment filled with proprietary software and poorly documented interfaces, open source development frequently relies on reverse engineering to fit in. Anyone who has used Samba to bridge Windows and non-Windows networks has benefited from Andrew Tridgell's reverse engineering of the Windows protocols for network services; anyone who exchanges files to read and write them in OpenOffice.org rather than Microsoft Word appreciates the reverse-engineering-derived ability to edit files in Microsoft Word format.

Courts have long held that reverse engineering, the practice of examining something and taking it apart to figure out how it works, is a fair use, not an infringement of copyright. Even when programs are released only as closed, binary code, programmers can often discover a great deal about them by watching their operation or the file formats they use, or by disassembly. Reimplementing those discoveries in new code comports with copyright too. So, companies have been protected in taking apart a video game console to build a console emulator (Sony v. Connectix) or disassembling a game to build a new one compatible with the console (Sega v. Accolade). If someone builds a better mousetrap after examining those that exist, copyright law will not stop her from deploying it.

At least that's the black-letter law. In practice, though, many copyright holders try to extend copyright's limited monopoly to block reverse engineering, through a combination of copyright, contract, and anticircumvention. For example, Blizzard, maker of the popular Starcraft and Warcraft video games, claims that all players have "agreed," through click-wrap licenses they encounter before the programs run, to a contract that prohibits reverse engineering the Blizzard games. This contract plus copyright, Blizzard asserts, prevents anyone from interoperating without permission.

The bnetd project began when a group of programmers became frustrated by the poor performance of Blizzard's battle.net server for multiuser play of the games they had bought. Instead of putting up with the frequent downtime and rampant cheating on Blizzard's server, they started work on their own open source game server. By watching the communications between game and server, the bnetd programmers were able to reverse engineer their own compatible server, which they set up to give owners of Blizzard games an alternate place to meet, and made the source available for others to join the effort. The public got another option for playing Starcraft, and another reason to buy Blizzard games.

Blizzard rewarded the bnetd team's creativity with a lawsuit claiming, among other things, copyright infringement and breach of the click-wrap contract. The team had not seen any of Blizzard's source code, much less copied it, as they reimplemented uncopyrightable functionality, but that didn't stop Blizzard from pulling out the copyright sword. Copyright's lack of protection for functionality is deliberate and sound innovation policythe public benefits from being able to choose among competing implementations of functionality, be they game servers or network servicesyet Blizzard follows in the steps of many trying to get around copyright's limits with contract claims.

Blizzard was trying to limit the code others could produce, to extend the copyright protection on its own code. But many of those pulling out copyright's swords aren't trying to protect code, but other copyrighted content touched byor that they're afraid will be touched bycode. These efforts, assertions of secondary liability, anticircumvention regimes, and attempts to impose technology mandates, all limit open source developers' ability to produce new code, to learn from old code, and to compete in the market with proprietary code.