Whose claim is touch-move?

Well, is it just opponent´s?

4.8      

A player forfeits his right to claim against his opponent’s violation of Articles 4.1 – 4.7 once the player touches a piece with the intention of moving or capturing it.

So, if an arbiter witnesses a violation of touch-move, and the opponent does not care and responds to whatever move the violator ended up clocking, is the arbiter allowed to interfere, or is this end of the matter?

A lot depends on which federation you are talking.  FIDE, USCF, BCF, etc, all have different rules about that.

For example, in USCF, the director can't ever call an illegal move.  It's up to the player to do it!

What I consider unfair about USCF rules is that the arbiter still can't call it even when the player isn't at the board at the time! This has happened to me once: I had reached a lost position, and went to the bathroom. Later, someone told me that my opponent had touched a piece, and even though the arbiter was standing there, he couldn't say anything. The move my opponent intended to make was a horrible blunder.

Needless to say, I lost the game.

I think you are asking a couple of different questions here. The rule you quoted basically says that if your opponent violates one of the listed rules and you don't claim that violation before you touch a piece with the intention of making a move, then you can not claim the violation.

I'll have to look at the rules but I believe if a FIDE arbiter sees a violation, in a FIDE rated event, then they are required to intercede.