GCJ with OpenJDK Java API instead of GNU Classpath

Forgive me if this is a silly question - but I wanted to ping the list 
before spending any time/effort here.

Grabbing GCJ's standard source releases, one can see that GNU classpath 
is integrated.   I've actually used classpath a lot and its a very 
stable API for me.

However - given recent events, particularly the 'freeing' of Java 
sources by Sun - is it a good idea to attempt to use Sun's 'official' 
Java API sources instead?  This would give the option of maximum Java 
API compatibility but also giving the ability to precompile native code 
using GCJ (which you cant do with OpenJDK afaik)

So my questions:

- Has anyone already attempted building the OpenJDK java sources with 
GCJ/and/or tried to swap out classpath for those classes?
- if not are people interested in going down this path? I am willing to 
put some efforts here.
- Are there licensing issues with linking OpenJDK to other code via GCJ? 
 From what I remember 'linking' is a touchy area with some FOSS licenses.

Thanks much in advance for any tips!!

- Sal