JAXB is part of the Sun
Java Web Services Developer Pack. Within the pack are separate sections for jaxb, jaxp, jaxm, jax-rpc, jstl, and saaj. Each section has its own jars. You can pick and choose the code you want to use from these sections, but there may be some dependencies between them. For example, when last working with JAXB I needed to include the JAXB and SAAJ jars, but not any of the jars from the other sections. I have not heard of any non-Sun JAXB implementations - please let me know if anyone else has.