Utility functions are a way of characterizing preference orderings between events. If a preference ordering satisfies certain properties, then there exists a utility function such that its expected value over the events can be used to decide which events are preferred over which other events (see VNM theorem). Utility values are not defined with respect to anything else, they are not money or happiness or resources. In particular, utilities of different players can’t be compared a priori, without bringing in more structure (for example redistribution of resources in the setup of Kaldor-Hicks improvement establishes a way of comparing utilities of players, see the original comment).
If you add a constant to a utility function, its expected value over some event increases by the same constant. So if one event had greater expected utility than another, it would still be the case after you add the constant. This is the sense in which adding constants or multiplying by positive factors makes no difference.
If you are a program and want another program to behave in a certain way, CDT doesn’t really help with setting up a way of solving this. Decision theory is about figuring out how decision problems should be solved, but it’s not in general clear what a decision problem is, or what counts as an admissible way of solving it.