Final answer:
The Supreme Court case applicable to the situation of two software companies attempting to merge is Northern Securities et al. v. United States, which addressed antitrust issues.
Step-by-step explanation:
Given the scenario of two large software companies attempting to merge and possibly dominate a major part of the software market, the most applicable Supreme Court case from the list is E. Northern Securities et al. v. United States. This case is a landmark in antitrust law where the Supreme Court addressed business practices related to monopolies and competition. The decisions in cases such as Dartmouth College v. Woodward, McCulloch v. Maryland, and Gibbons v. Ogden collectively suggested that the federal government has a role in economic development and in the regulation of commerce, supporting a broad view of federal power.