Thank you for posting your question.
The OutSystems platform hosts its applications in its own application server. If you've installed the Community Edition, the platform server is placed in your own machine. This means you deploy your applications to your localhost.
The system requirements for installing the OutSystems platform can be found here. You can also opt for a virtual or cloud hosting service such as Amazon EC2. Just be sure the minimum requirements are available on your server instance. Outsystems only provides hosting services for development environments if you're already a customer with a license.
Regarding your last question: absolutely, all OutSystems deployed applications are 100% .net/java code, since the platform server runs over one of those technologies.
Let me know if you have any other questions or comments.