What would be the best way to simulate a linked source?

Solutions:

1. game.ReplicatedStorage.SomeScript:Clone().Parent = script.Parent; script:Destroy()
2. ModuleScripts (you could put your code in the ModuleScript, wrap it in a function, and call it; see below)
3. Redesign your scripts to use tables/lists instead of copy/pasting your script for each item (you can also use ModuleScripts as collections of functions and/or places to hold data to be shared amongst multiple Scripts)

ex. Let's say you have a script that just keeps changing the transparency of its parent and want to change it so you don't have to copy/paste the script:

--Before
local p = script.Parent
while true do
	for i = 0, 1, 0.1 do
		p.Transparency = i
		wait()
	end
	for i = 0.9, 0.1, -0.1 do
		p.Transparency = i
		wait()
	end
end

--Option #2, ModuleScript:
return function(script)
	--above code here
end

--Option #2, calling script:
require(game.ReplicatedStorage.TransparencyScript)(script)

--Option #3, central script:
local ch = workspace.Parts:GetChildren()
--or if the parts aren't all in the same place:
local ch = {workspace.Part1, workspace.SomeModel.Part2, --[[etc]]}
while true do
	for i = 0, 1, 0.1 do
		for j = 1, #ch do
			ch[j].Transparency = i
		end
		wait()
	end
	for i = 0.9, 0.1, -0.1 do
		for j = 1, #ch do
			ch[j].Transparency = i
		end
		wait()
	end
end

I recommend option #3 as you can script which parts to use, rather than having to copy/paste the requiring script in option #2; it also is easier to coordinate changes to multiple objects when it's all handled in the same script. ex, if in the above scenario you wanted to make it so that the 2nd object was a bit delayed in its transparency changes compared to the 1st, there are ways to do that, and you'd only have to change this one script.