Map Reverse Converter is needed only if you are unlocking maps in MapSource with Garmin Unlocker (All.bat), it has nothing to do with unlocking image files.
Don't worry, for now you can use unlocked maps safely. Any map could be locked, and not locked. Unlocked map is map that is actually locked, but has unlock code inside or in unl file which Garmin device (or program) is using to unlock map.
There could be way to device (or program) as new versions of MapSource, MapInstall and UnlockWizard, analyze this unlock code and detect it is illegal.
When map is unlocked with this tool (or Fast IMG unlocker, or Garmin Unlocker - All.bat) it has actual status not locked, so any Garmin device or program could not "see" that it was locked at any time, and "thinks" it was never locked, so for now, no way to find out it is illegal - no unlock code to analyze.