A separate map is required for each project. MindGenius will always open separate maps in individual windows, allowing you to make comparisons by displaying separate maps side-by-side or on different monitors.
It is not possible to display multiple projects within a single MindGenius map.
All MindGenius map styles are based upon a single "core" branch, meaning that every branch or task in your map or Gantt chart would have to share a common core branch. That would make it difficult to separate tasks and would cause problems with the roll-up of task properties between tasks and summaries.