This is the grey area of emulation. HTGDB distributes links to ROMs and ISOs. While the structure and metadata (the XML files and art) are legal creative works, the games themselves are often copyrighted.
The general rule of emulation applies: Do not download ROMs for systems you do not physically own the original hardware/software for. That said, for "Abandonware" systems (like the Amiga CD32 or MSX), copyright holders rarely enforce their rights, but technically, the legal risk rests with the downloader, not the curator. Htgdb-gamepacks
The most famous feature of HTGDB-gamepacks is the single download file for full console libraries. For example, instead of downloading 700 separate PSP ISO files, HTGDB offers a single torrent or archive containing the entire PSP library, split into manageable chunks but logically unified. This is the grey area of emulation