Removing a signature from a Jar file like JAXB is easy.
Just go to the meta-inf folder, find the Manifest.mf file and remove all the paired lines Name & SHA1-Digest.
Save that and update the jar file with the changes.
THer might be also other security related certificates in the meta-inf folder that can be removed too.
But pay attention to what you are doing! Downloaded
Java executables from vendors like SUN, BEA or IBM are always legally protected. Check the licence to see exactly what you can do with that software. JAXB in particular comes with an "evaluation purposes only" licence.
I have been answering to E-mail and bloggin about this:
Why an Open-Source policy? JWSDP licence If I remember well, there was a conflict within the javax.xml.namespace package where there were classes signed by Sun and unsigned classes.
Maybe just removing the conflicting jar file (xml-namespace.jar or something similar) was solving the problem I had because an implementation of the class in that jar file was existing already somewhere else.
Robin