As a quick aside, “them” is an object pronoun, not a subject pronoun. The correct word you needed is “they”.
You couldn’t phrase your original question as a statement “Them have though.” That’s often a quick test for valid English grammar. With the correct pronoun, it makes more sense: “They have though.”
As another example, take this sentence: “Have you seen them though?”
“You” is the subject of that sentence, and “them” is the object.
It's short for "Have them [Node bozos improved it], though?"
Or, equally likely it, refers to deno and bun ("deno and bun has really made Node focus and improve", "Have them (deno and bun) really made Node focus and improve, though?")
You couldn’t phrase your original question as a statement “Them have though.” That’s often a quick test for valid English grammar. With the correct pronoun, it makes more sense: “They have though.”
As another example, take this sentence: “Have you seen them though?”
“You” is the subject of that sentence, and “them” is the object.