What happens to the energy from a GRB? A gamma ray burst produces somewhere around 1044 J of energy, according to Wikipedia. Only a small portion of that energy will be absorbed by other objects.

The rest of that energy will go on to travel the universe indefinitely I presume?

How do we know how much of the universes total mass-energy is in "in transit" in the form of gamma rays and other forms of radiation?
No energy is in transit as GRBs, just like Gamma rays that started in a GRB.

If you remember that all that energy is in the form of radiation, it obeys the same laws as ordinary light: the farther, the dimmer (inverse of square of the distance law).

So if you see stars dimmer as they are farther from you, same happens to the RGBs. Radiation from the stars expands infinitely (becoming dimmer and dimmer) until absorbed by clouds or just becoming dimmer than the background.

Same happens to gamma rays from GRBs. It is just that since rays are more energetic, they are less easily absorbed, and since GRBs themselves are more energetic, the becoming dimmer than background distance is bigger.