So I've done some more research on Dead Dev Games, and I still haven't found much...
However. something had happened while doing my research. Last night while I was looking up what Dead Dev Games could be, I suddenly got an alert from my Steam application. I open it to see what it was, and I find a friend request from a person named "Po". I accepted it because I don't have any Steam friends myself...
A minute later, I received a Steam message from Po.
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Po: I saw your portal mod on moddb. you are the creator right?
Yes, I did compile the source mod together. Thanks for giving it a look!
Po: I see. i also saw your blogs. Stop looking for us. you don't need to know anything else about us.
Are you part of Dead Dev Games?
Po: Yes i was at one point.
Po: Ill update your game since you cant get it back. i dont know how you got a hold of our project.
Wait, what do you mean by updating it?
Hello?
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An hour later, I found out that Portal had an update. I don't know how, but Po had somehow managed to delete my version of the game and update it to the actual latest version; the normal version, if you will. It's a good thing I had backed up the files before then, but I think it's clear that whoever these people are don't want me to look into this project.
Either way, we'll see what happens after this. Hopefully I can find more info on what's going on. But at the same time, hopefully I don't...