It is a damn shame this system is not available to the DIY market. Say what you want but any system is better than no system and a very high percentage of home owners cannot afford $75-$150/hour for a plumbing contractor to install a system. I am a master electrician and I am pretty damn sure with the design work done for permitting I could handle installing that system. It is certainly easier than sweating copper or threading black iron.

Can it be retrofitted in an older home.

May I suggest that you tone down the volume on the video so that you can actually hear the narrator?

If it’s a permitted plan and properly inspected, I don’t see how diy installation differs from one by a licensed installer. I’ve seen incompetent uninspected work performed by both as well as good permitted work. Plus for the homeowner, it’s a matter of life and death - for an installer it’s a matter of profit and liability.