What are the guidelines for deploying the Antlr runtime libraries using applets, Java Web Start or other technologies that required jar signing?

Our interpretation of the Antlr License is that jar signing would be forbidden since it constitutes a modification of the distributed binaries. Is that the case?

It's ok with me if you include the antlr.jar files. You would be signing the jar, but not the binary files themselves. The license is primarily talking about the .class files, not a ZIP or jar of them. As I understand the license, you are free to sign those jars.