I am a long time ArmA modder. Ever since I've put my hands on RV games I always tilted towards the modding scene. One of the shortest yet most impactful points I've heard in the GameStar interview was "With BETA comes modding".
I don't know how long is it until BETA hits and it doesn't really matter to me right now. What I do wish to know is as much information as the devs can share about it.
Here's some more personal speculation/conjectures from me..
First off, I'm referring to this: https://www.twitch.tv/videos/169133158?t=08h15m50s (15 seconds)
There are lots of scripts in the client files which are being used (some that aren't), so what Eugen says is demonstrably true. The scripts are identical to C++ (and use .c as an extension) with the exception of not having #includes (presumably because scripts are restricted to the interpreter). For further proof, it's been said that stones will spawn physically on the ground in 0.63 rather than only found in the "gravel textures," but the script for stone generation already exists, so this is a very recent addition. (Spoiler: 5 stones around each player, 60 meters in front of the player and with 15 meter radius)
This would mean, we really will have access to the majority of the game, like in Take On Mars. Also, one educated guess I would make is that DayZ will use the Workbench editor from ToM. There are a couple references to it.