So how do I make sure the jars are mounted?
By mounting them yourself in your deployer. :-)
I think they will not be double mounted, and also make sure you unmount them as well.
Also, I started looking at your AS6 changes for the Seam deployer. Should I extend from UrlIntegrationDeployer instead of AbstractSimpleVFSRealDeployer?
No, as that one doesn't do much else than what you're already doing.
I probably need to think if I should also already do the mounting.
I'll probably make it optional, so a user can choose, dependening on when he needs these new resources.
btw: when do you need -- at which deployment stage / state -- these new resources?