WIP
As a broad phrase, copyright infringement relates to actions which 'infringe' on, or violate, a 'copyright' held by another party, usually a corporation or company in this context. The most common form of copyright infringement in the gaming community is software piracy, which is where a user downloads software from somewhere other than the copyright holder's authorized distribution channels, and most commonly without payment to the copyright holder (or their delegate).
Piracy in the context of the gaming community can be simply defined as 'downloading paid software for free'.
Copyright infringement (whether infringement of paid software or free software) is against the law in most jurisdictions, including the United States. As a significant amount of online services (not least of all, Discord) are based or hosted in the United States, they are obligated to follow United States laws.
Due largely to the concept of 'lost profits', copyright holders have (in many cases successfully) lobbied relevant governments and powers to make it illegal, or at least frowned upon, to install homebrew/CFW. Continued copyright infringement legitimizes their efforts, de-legitimizes the homebrew community at large, and makes it more difficult all around for both developers and users in the homebrew community.