Is data used by EveHQ stored somewhere on the hard drive where they can be accessed by other third party program?
The API data that EveHQ downloads is cached on your HDD so is available to other programs if you require. They are stored in the Cache folder in the Application Data folder. Each API should be labelled with its function and the general format is: EVEHQAPI_APIType_UserID_CharacterID.xml. Obviously some APIs don’t require characterIDs or UserIDs (e.g. SkillTree.xml) so these parts will be missing from those filenames.