I sent an application for the Spellguard, and I still haven't received a reply from a DM. Do they reply to all the faction applications?

I am not a DM, but generally speaking, faction applications do not get responded to.

You must persue the faction you are seeking to join in game, and you will discover in game whether or not you are going to be accepted to the faction. If you have not already, I would recommend that you start interacting with some of the Spellguard players (not the NPCs). I think you will quickly discover the path to becoming a Spellguard in game, and the actions you take directly influence the success on that course.

Applying, and then persueing membership in game is basically the procedure for any npc faction.

If you have IRC you can join #efuapps and ask about the progress of your application.

We may hold our verdict for faction applications back until we decide to give you membership in game, in character, but applications for things that require you to make a character from scratch will get a response straight away, or as soon as posible.

I must say that IRC is likely the best way to get in touch with a DM, or atleast myself. You can get a free IRC client at http://mirc.com/. If at first it does not work (likely because you have a firewall), there's plenty of troubleshooting advice people can give.