Ethical alternative : Use official (free for U.S. waters) or S-63 charts from your national hydrographic office. OpenCPN handles both perfectly.
Assuming you have a legitimate or archived copy of CM93 charts, here is how they are typically installed and configured in OpenCPN, the most popular software supporting this format. cm93 v2 charts download install
For a terrifying ten seconds, nothing happened. Then, suddenly, the blank blue canvas of the screen flickered. Ethical alternative : Use official (free for U