The news has been filled recently with game companies using legal means to go after trademark and copyright offenders who infringe on classic and retro intellectual property. The latest to come across our news feed is that Taito (now part of Square Enix) has been "all up in Mochi's grill", asking that they remove all games named Space Invaders and any game that uses its unique visuals or sounds. The area of patent, trademark, and copyright law is murky when it comes to video and computer game entertainment, so we can't officially tell what exact games they might be targeting.
It's always a good idea to use your own graphics, sounds, and names in your games, even if you are making a "tribute", especially if it is for commercial use. Game play usually is not something to which a copyright can be applied, but patents can be applied to systems and algorithms that solve specific problems. There is a lot of confusion over on this Mochi thread. If you have any insight into what is going on with Taito, or just on the various laws involved, please leave it in our comments, or hop over to the Mochi thread and let people know what you have to offer
And now, just in case you missed it the first time around, here is our classic take on the situation.
Skript Kitty Vs. Intellectual Property