Yes, OSGi uses that dusty old META-INF/MANIFEST.MF file. For years, that file has resided in every JAR file you've ever made, but it never received any love. But OSGi needed a place for metadata and decided to give MANIFEST.MF something to do. So, now MANIFEST.MF has found new life in OSGi.
Fortunately, given tools such as BND and Pax Construct, you almost never have to deal with the MANIFEST.MF directly. Instead you can let most of it be auto-generated.