Jacobsen v. Katzer was an important court case in the United States. It involved a computer programmer, Jacobsen, who wrote some computer software that was made available to the public for free. Katzer was a company that took Jacobsen's software without permission and tried to sell it for money.
Jacobsen was not happy about this and sued Katzer. In the court case, a judge looked at the law and determined that Jacobsen's software was protected by copyright law, which means that nobody else can use it without permission. The judge ruled that Katzer was wrong to sell Jacobsen's software and had to pay Jacobsen money for taking his software without permission.
This case was important because it showed that people who create software or other types of works can protect their work from being taken without permission and used for another person's benefit. It also showed that software companies can't just take other people's work and use it as their own.