Correct me if there's missing information that disproves this, but the Roblox version was made in 2010, while the Gmod version was made in 2012. The names would suggest the Roblox version came next, so tell me if maybe the Gmod version was on something other than the workshop before 2010.

Update: I found the original ModDB version which came out 2 days before the Roblox version, though it also says it was the 'final version' so there could be older releases. If not, then did the creator of the mod also make the Roblox version?

Finally, got my answer, only took over 2 years.

Sorry, I only just found the Gmod version. Been playing the Roblox version since 2013, I had no idea there was a Gmod version. Explains why the Roblox version has a heavy Half-Life 2 presence I guess.

same.