How do I get into a non-password protected Java keystore or change the password?
which means that cacerts keystore isn't password protected
That's a false assumption. If you read more carefully, you'll find that the listing was provided without verifying the integrity of the keystore because you didn't provide the password. The listing doesn't require a password, but your keystore definitely has a password, as indicated by:
In order to verify its integrity, you must provide your keystore password.
Java's default cacerts password is "changeit", unless you're on a Mac, where it's "changeme" up to a certain point. Apparently as of Mountain Lion (based on comments and another answer here), the password for Mac is now also "changeit", probably because Oracle is now handling distribution for the Mac JVM as well.
The password of keystore by default is: "changeit". I functioned to my commands you entered here, for the import of the certificate. I hope you have already solved your problem.