If you pay close attention to the video, you can see FDS, Yak's Bend, a 'SAD' version of ascalon armor, and some other GW related material. However, the monsters do not really look much like monsters in GW.
Some of the comments on the video states it is the Alpha/Beta testings of the original GW, (before Anet joined NCSoft). It was said this is the test environment of GW just to test out matters such as damage, combat, and general game mechanics.
There are two problems with the stated theory above
1) I have seen videos from the alpha and beta testing that was made public, and they do not look like that.
2) How did this person get his/her hands on such videos and content? you cannot access really far adventures of the game in a beta testing.
Please help out on identifying its truth.
PERSONALLY, I was like : " NO Freaking WAY THIS IS GUILD WARS!!!"
PS: Now I believe this is the version of GW before the E3 event.