New BGH Case Law on the Modification of Computer Programs

In two rulings delivered on July 31, 2025, the First Civil Senate of the German Federal Court of Justice (Bundesgerichtshof – BGH), responsible for copyright law, addressed the issue of modifying computer programs.

Ad‑blocker (Judgment of July 31, 2025, File No. I ZR 131/23 – Werbeblocker IV)

An operator of several online portals contested against the distributor of a browser plug‑in designed to suppress advertisements on websites.

How the ad‑blocker works

The ad‑blocker interferes with data structures generated by the browser in a user’s RAM after fetching and loading the HTML file. It alters the object structure (the DOM node tree) as well as the formatting structures (CSSOM) used by the website, preventing elements recognized as advertisements from appearing on the user’s screen. This happens either by preventing ad content from being retrieved from ad servers or by loading it into memory without displaying it.

Copyright infringement through interference with protected code

The BGH held that the exclusive right to modify a computer program under § 69c No. 2 first sentence of the German Copyright Act (UrhG) and the exclusive reproduction right under § 69c No. 1 first sentence UrhG may be infringed if the browser and its engines are not controlled via object code, but by bytecode from which the browser’s virtual machines generate object code. That bytecode—or the code generated from it—may be protected as a computer program, and an ad‑blocker that alters this code in the course of reproduction may infringe the exclusive right associated with it.

Decision

The BGH referred the case back to the appellate court for a new hearing and decision, so that it can clarify which part of the website (bytecode or object code) is affected, whether it is protected by copyright, and under what conditions the interference may be justified.

Cheat Software (Judgment of July 31, 2025, File No. I ZR 157/21 – Action Replay II)

The distributor of PlayStation consoles and associated games challenged the “Action Replay PSP” software, which enables users to manipulate original games to bypass restrictions such as the limitation of the use of “boosters.”

How the cheat software works

Using “Action Replay PSP” requires connecting the PSP to a PC and inserting a Memory Stick. After rebooting the PSP, users can access an additional menu labeled “Action Replay” to deactivate in‑game limitations. The software runs concurrently with the game software and does not modify the object or source code or the internal structure of the game. Instead, during gameplay, it alters the values of variables that the game software stored in the PSP’s RAM and uses during execution. As a result, the game runs based on these modified variable values.

No copyright infringement without interference with protected code

The BGH held that the exclusive rights under § 69c No. 2 and § 69c No. 1 UrhG are not infringed when the cheat software does not alter the program data of the object or source code of the game, but only other elements such as variable data created in RAM during program execution. If only the program flow is influenced in this way, it does not constitute an infringement of the software copyright.

Significance of the Decisions

On the one hand, an ad‑blocker may infringe website copyright, even though it merely prevents certain content from being displayed. On the other hand, software that modifies the intended program flow of a video game is classified as non‑infringing. At first glance, this may appear surprising.

Criterion: Interference with code

The BGH draws a legal distinction based on whether the code is interfered with. The author of a computer program creates the code, and only if this code is modified is their right violated. In the Action Replay II case, the BGH found no modification to code, while in the Werbeblocker IV case, it deemed that not only the author-created source and object code may be protected, but also a bytecode running on a virtual machine that translates it into machine code.

As an aside: Programming languages without object code and platform‑independent programs

For instance, Java programs are not directly compiled into object code. Instead, they are compiled into bytecode executed on a virtual machine (part of the Java runtime environment), which translates the bytecode just in time into machine code for execution. This enables platform independence, provided the appropriate runtime environment is installed.

Extension to code not directly created by the author

Interestingly, the BGH includes code under copyright protection that was not directly written by the program author, but indirectly generated from code created by the author.

Application to AI‑created computer programs?

Application to AI‑created computer programs?
This development may be relevant for future considerations. It suggests that programs created using artificial intelligence might also be protected by copyright. This raises further questions: Who should be regarded as the author—the one who programmed the AI model, programmed the AI system, trained the AI system, or created the training data?