Is it possible to integrate the renderer into other applications? There does not seem to be any API to do so?
It is possible to integrate the renderer into other applications. If you look at OpenRPT/renderer/openreports.txt for some documentation about the renderer api. I am not sure if that file is completely up-to-date but should cover all the basic you need. In addition I would suggest looking at the source for OpenRTP/renderapp. This is the RPTrenderer application and is basically a front end gui to the renderer library.