(1) Can I develop a stand-alone software with the API? Here stand-alone means we embed some Inventors features in our software and our users do not need to install inventor to run our software.
Yes there are 2 options with developing a distributable software using the Inventor API in a standalone application.
(2) If yes for the above quesion, can I distribute/sell the software? Or I need a license from AutoDesk to do it?
Depending on what you're during with the API Inventor View may be all that's needed. Inventor View must be installed seperately but it is free. It won't allow you to make any geometry or modeling edits but you can make file reference changes and query the model. (The API help file explains the differences.) In order to have full Inventor functionality in a standalone application you need to use Inventor OEM. Not sure what the costs are associated with this but I'm sure there are some.
(3) If no for the above quesion, I can choose to develop an add-in on Inventor. Can I distribute/sell the add-in? Or I need a license from AutoDesk to do it?
No you do not need a license to sell an stand alone application or add in. You can also sell addins through Autodesk's Exchange Store. Ypu can't redistriubute any of the Autodesk software with your application/addin. You can do whatever you want with you software.
