OSGi Alliance Specifications
OSGi Service Platform Release 4
OSGi Service Platform Release 4 was first released in October 2005. Version 4.1 was released in May 2007.
You can also order the Release 4 specifications in book form at aQute Publishing, for members see the OSGi page for a discount.
OSGi Service Platform Release 3
OSGi Service Platform Release 3 was released in March 2003.
You can still order the OSGi R3 release in book form from Amazon or if you are a member, send a to obtain a discounted copy.
OSGi Service Platform Release 2
OSGi Service Platform Release 2 was released in October 2001.
OSGi Service Gateway Release 1
OSGi Service Gateway Release 1 was released in May 2000.