ALA is supportive of the liver, some brands of ALA are natural compounds, same as the body naturally makes. ALA is an important substance already made in the body, it is not "alien". It is used by the liver, it does not add to the liver load/stress. To confirm this do a Google on "ALA liver". ALA is liver friendly.
DMSA on the other hand is an "alien" substance, it is not a natural made substance in the body, consequently it is "processed" by the liver before it is excreted, thus increasing the load/stress on the liver.