Please use the following links to download the specification.

OSGi Core Release 5 Specification 
OSGi Core Release 5 Companion Code 
OSGi Compendium Release 5 Specification 
OSGi Compendium Release 5 Companion Code 
OSGi Enterprise Release 5 Specification 
OSGi Enterprise Release 5 Companion Code 
OSGi/Minimum-1.2 Execution Environment 
CDC-1.1/Foundation-1.1 Execution Environment