jakeyiii, please avoid double posting, as it is against the forum rules. You can review our forum rules here. Thank you.
If by "Sources" you mean the programming source code - the entire game engine script is visible when you open the script editor in the game editor.
The game editor itself is NOT open and you'll finde no code from it, but that isn't neccessary as the game's code is fully visible in the script editor.
You might also search the forum for previous discussions on multiplayer and network gaming, there have been discussions about how to program such a thing in the past.
One warning: If you really want to do that, then you're looking at several months of full-time work, because you have to start from scratch/zero.
There is exactly one script available for basic online operations like managing a highscore (look for it on the master script list), and that is not enough for online gaming.
And a server for online gaming is also needed - you need to program that as well because nothing like that exists yet.