Harmonix and Konami have been suing each other for a while now - Konami thought Rock Band was a bit too similar to a patent they had, while Harmonix thought that Konami's Rock Revolution in turn was a bit too similar to their games and all of the sudden we had one big suing party going on. As it should be, but now it seems like the two parties have decided to make peace with each other, according to Bloomberg.
There might have been a settlement between Konami and Harmonix, but no details are known at this time.