The maxim ‘Pacta tertiis nec nocent nec prosunt’ is a principle in international law of treaties which translates to "agreements do not harm or benefit third parties." This principle implies that treaties are binding only on the parties involved in the agreement and do not impose obligations or confer rights upon non-parties, unless the third parties agree to such terms separately.
Thus, in the context of the given options:
Considering both explanations, the most comprehensive understanding of the maxim is captured by the option "Both (a) and (b)" as it encompasses both the binding effect of a treaty only on its parties and the non-imposition of obligations on non-parties. Thus, the correct answer is Both (a) and (b).