There is currently no way to get the issue type scheme for a project via the SOAP APIs. My use case for this is for a help desk portlet that I'm developing for our companies portal. It should use SOAP to get the issues associated with a project so support staff can easily add new issue types to the project (i.e. printing, email, etc.). Right now we have to statically configure the portlet with the issue types that should be used for help desk tickets. The preferred way is to get the issue type scheme for the help desk project in JIRA and allow the user to select from those.