Dear Dale,
The Revit API help does not have anything to say on this subject, as you can see under Developers > Revit API Developers Guide > Introduction > Add-In Integration > Add-in Registration:
http://help.autodesk.com/view/RVT/2015/ENU/?guid=GUID-4FFDB03E-6936-417C-9772-8FC258A261F7
I asked my other colleagues, and they concur with Augusto saying:
Yes, that is the theory; Max, Maya and AutoCAD (at least) use C:\ProgramData\Autodesk\ApplicationPlugins.
As long the host app looks in that folder, it should work.
I’ve just checked and this location (C:\ProgramData\Autodesk\ApplicationPlugins\...) works for Inventor 2015 AddIns as well.
The Inventor API Help describes four recommended locations:
1. All Users, Version Independent
- Windows 7 - %ALLUSERSPROFILE%\Autodesk\Inventor Addins\
- Windows XP - %ALLUSERSPROFILE%\Application Data\Autodesk\Inventor Addins\
2. All Users, Version Dependent
- Windows 7 - %ALLUSERSPROFILE%\Autodesk\Inventor 2013\Addins\
- Windows XP - %ALLUSERSPROFILE%\Application Data\Autodesk\Inventor 2013\Addins\
3. Per User, Version Dependent
- Both Window 7 and XP - %APPDATA%\Autodesk\Inventor 2013\Addins\
4. Per User, Version Independent
- Both Window 7 and XP - %APPDATA%\Autodesk\ApplicationPlugins
I hope this helps.
Cheers,
Jeremy