Updating from a DVD is possible. You just need to add your DVD as a new reposity to your yum's configuration; I believe there are ready tutorials on how this is done, so I don't interfere in that (because I'm not 100% I remember it correctly). But the key question is: how you configure DVD as a yum reposity? Ask that from Google
If you mean is it possible to download software from Fedora's reposities (ftp) and install them on non-Fedora system, yes and no. It depends. If the distribution you use is very close to Fedora you can try, but you might mess up. On a completely different kind of system, say Debian, I wouldn't try since on Fedora the packages might get installed into other places than on the other system, so in the end you could just break something; better use distribution's native packages or compile from source.