There is surprisingly little information on the internet regarding what Moonlight is exactly from a technical point of view. Is it correct to understand it as Mono-based CoreCLR + base libraries (the same .dlls as Silverlight has as part of the plugin itself)?
Does this mean that if I have Silverlight 3.0 application and I reference base library, plus develop my own Silverlight libraries, this application will work the same in Moonlight 3.0 (when available), except for bugs, etc., of course.
Yes, your Silverlight applications should run with moonlight (modulo bugs, yeah). From moonlight-project.com:
Moonlight 2.0 should be out soon and there's already work underway in supporting Silverlight 3.0 features.