Yes, it is the OFFICIAL version
Here is the first page:
You can find out more on this reddit post, including email with one of the people who works on the official comic and a preview of a part of the script.
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Very apt of them to start off by showing the TF2 community after waiting so long for an update
HL3 enjoyers
WHAT
The day of prophecy has come to pass. All TF2 players please report to your nearest mountain so you may ascend.
Holy shit
Oh, wow, at this point, I had been waiting for this more than for something like HL3
poggers
THERE CAN BE MIRACLES! WHEN YOU BELIEVE!