Thats false! There is already a link to the wikipedia article, but here is the relevant quote: „but uses hardware restrictions or digital rights management (DRM) to prevent users from running modified versions of the software on that hardware.“
It is not a violation of the GPL 2, the license of the Linux kernel, but only the GPL 3 which was basically created for this case. Linus Torvalds is a big defender of the GPL 2 and said that Tivo provided good patches for the hardware they used.