Download the installer from MAS, it's a .app within which you'll find a `createinstallmedia` binary. As its name indicates, that binary can be used to create a bootable install media. Not sure it can create a DVD, but it can create a bootable USB key.
You can't download an ISO, you'll need a working OSX install to download it from the App Store. From there I believe you can burn an install DVD and AFAIK you've always been able to do a non-networked install.
edit: Un-tested by me, but I've heard this is how you do it:
As of Mountain Lion, the recovery partition doesn't contain the full OS. Just enough to bootstrap and download the whole thing from Apple. They also do not sell the update on physical media (thumb drives, DVDs, etc.) in store.
Lion DiskMaker has a beta for creating a Mavericks GM disk. It should be updated soon to support the release. You just download the installer from the App Store and run Lion DiskMaker.
sudo "/Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia" --volume /Volumes/Mavericks/ --applicationpath "/Applications/Install OS X Mavericks.app"
Note the double hyphens before the keywords. The quotes just make it easier to read.
Probably the same way as I've done with Mountain Lion, but with a dual-layer DVD instead: http://www.techrepublic.com/blog/apple-in-the-enterprise/how... (not that exact link, but the same basic thing is all over the internet) If you want to do this for an older OS version you've purchased, you can option-click on the Purchases tab-button-thing in the App Store, and it'll show everything. (totally undiscoverable, but at least it exists)
I'd like to burn a bootable DVD, and load it up as a non-networked offline install. Is such a thing even possible?