It's almost as if though they're not supposed to mess with the mass of the moon which would change its orbit.
LOL. The Moon's mass is roughly 73.4 sextillion metric tons.
Let's say you built a moon base that weighed 1,000 metric tons. It would add 0.000000000000015% to the Moon's mass. That's not even measurable.
If you launched all the material mined on Earth in an entire year (about 100 billion tons) and piled it onto the Moon, it would still only change the Moon's mass by a negligible 0.00000014%.
And even if the amount of mass added was significant, the mass of a satellite (whether it's the Moon or a feather) does not affect its orbital path. The movement of mass from Earth to Moon might shift the Barycenter (which is deep inside the Earth) perhaps the width of an atom or less. Basically unmeasurable and certainly negligible.
Don't lose any sleep over the Moon's orbit. It's known natural orbital change (it drifts away from Earth a couple inches per year) far exceeds anything we humans can do to it.
LOL! Are you afraid it's going to tip into the ocean?!?