As I replied in the other thread, loading resources from the stream is different then resolving them. The OSGi platform is always going to use its own URL schema no matter how you try to pack things up - if the library expects just file:// or jar:// then this is not going to work.
Regarding the bootpath delegation, I'm sure there are other examples on the internet as well. Try to use various startup combinations and as a simple test, double check what packages are exported by the system bundle.
Also, make sure the packages that you export are available on the startup classpath since otherwise the platform does delegate but it cannot find the classes requested.