A. Java SE 6. Versions prior 2.2 also run on Java SE 5.0.
A. Metro includes JAXB RI, JAX-WS RI, SAAJ RI, SJSXP, and WSIT, along with libraries that those components depend on, such as xmlstreambuffer, mimepull, etc. To simplify the handling of jars, jar files of the relevant components and libraries are repackaged into a smaller number of jar files. See META-INF/MANIFEST.MF of Metro jar files to find out the exact versions of the components in it.
A. Please note: What follows is simply a high-level description of the licensing terms, not a legal advice. Please talk to your lawyer for the detailed legal consultation.
Metro is released under the dual license of CDDL and GPLv2 with classpath exception. What that means is that as an user, you only need to accept one of the two licenses.
A. Look for Build-Version manifest attribute in META-INF/MANIFEST.MF. This file is available in all the Metro jars.