Creating a (usable) backup of a soon failing data carrier should be legal either way. Yeah, a lot of countries have stupid laws there, but as long as you don't share the data on the internet, you should be fine.

Also to note: to legally watch a DVD, you require either Windows or MacOS, with a supported (proprietary) player software, in most jurisdictions. So, there, no legal DVD for Linux (or Haiku, Android), laws are stupid. And instead of cracking it on each watch, better to just do it once.