This page provides information about this screen, which is displayed for certain ROM hacks that you play.
This message displays as a preventative measure to ensure that ROM hacks are not sold. Generally, the authors of ROM hacks spend a lot of time with the hack for non-profit purposes. However, this hard work can become the fruit of another's profits. Think of, say, a new home brew device you've just made. If it was stolen and a person sent it to a mass-production line and made profits off your work, would you be pleased at all?
Most Pokémon games are sold in retail stores or on trustworthy resellers. eBay is not necessarily a trustworthy source for games. Legitimate Game Boy Pokémon games will often have a colored case (and with the exception of Red, Blue, and Yellow, a holographic label) - in the case of the Advance games, these are clear plastic cartridges. (Pokémon Pinball Ruby & Sapphire is an exception to this - it has a gray cartridge.)
Most Pokémon ROM hacks are available on many websites such as The PokéCommunity for free. Hacks are generally made as hobby work, not for profit.
You haven't been ripped off if you haven't paid to play a ROM hack. (Finding the ROM is free, but not necessarily legal.) If you buy a ROM hack, it may be incomplete. Some authors may not offer support for the hack. You certainly can't get help from Nintendo, either. If you do buy a hack, when it could be provided for free, you should return it for a refund - it may be necessary to approach a Consumer Affairs office for this.
© 2007-2008 Hiroshi Sotomura