I was wondering how this affects the current installation of DAoC. I have that through DR. If I want to play on one of the shards, do I need to download the trial also? Then use that installation to play the shard? I don't want to mess up my installation of the registered game....

Playing on freeshard does not affect your live installation. You simply use another launcher.

Being able to play depends on the number of the current version. Shortly after a live upgrade, you will have to allow some time for the current version to be playable on freeshards. At the moment, US live version is 1.82. This is also the highest playable version for freeshards. However, 1.83 is already being tested in US.

Sorry if I"m being dim-witted here. So what you are saying is that I use the current installed files, and simply a different launcher? Or do I need to download another instance of DAoC also? I've heard that you need to be patched to the EU version, does that mean that it will change my current files?

you only need a different launcher (use searchbutton), normally every version is playable,some have got probs,but mostly the german ones..(climbing walls etc)

If you want to be on the safe side, you could replicate your DAoC installation, but this is not required. (You don't have to reinstall, though. Just copy your current installation and downgrade by editing update.dat for the European server, if necessary.) As I have said earlier, you might get troubles when the US version takes the next step (until the new version will be supported by the launcher again). The European version is usually one or two steps behind, so this makes using freeshards easier (a current European version is practically supported all the time). I myself use a 1.81 US installation to connect - without any problems. I also know of several people already playing with 1.82 US.

[Note: Since 1.82 introduced town updates for Cotswold, Mag Mell, and Mularn some NPCs might be slighly misplaced at their pre-1.82 locations.]