Before Activision and Red Octane's Guitar Hero, there was Konami's Guitar Freaks which also made use of its own guitar peripheral. Konami already holds patents which essentially outline Guitar Freaks' gameplay with a guitar controller. While Activision purchased patents of their own relating to rhythm action around August 2006, they were not specifically related to guitar gameplay (in fact, they concerned drums).

Interestingly, eagle-eyed gamers have noticed that references to both Activision and Konami's patents appear on Guitar Hero III's loading screens, which could strongly suggest Activision may have gotten in contact with Konami to become a licensee of their patented technology. Lawyer S. Gregory Boyd certainly draws a connection:

"It is clear that Activision and Konami must have some sort of licensing arrangement for the Guitar Hero series. The United States Patent and Trademark Office public assignment databases show that some of the patent numbers listed in the Activision notice for the Guitar Hero series are not owned by Activision. We can also see that some of the patents in that list are now owned by Activision, but were recently acquired from third-parties. The other patents in the notice are owned by Konami.

...there is some sort of license in effect, but we cannot know the terms of that license or the nature of the negotiation. One cannot tell if money changed hands, if there were threats of litigation, or if there was a cross-licensing agreement. All of these are common, but impossible to tell from the publicly available information."

If Activision did in fact have to go to Konami for guitar gameplay licensing, are Electronic Arts and former GH developer Harmonix already doing the same for Rock Band?