Compiling Code.
Why not ask for encrypted DM that can be compiled? Like this nifty tool - http://www.javascriptobfuscator.com/Default.aspx Or the many that are available ? obviously no one could decrypt it without the "key"
#include "http://byond.Forum_Account/Pixel_Movement"
What it sounds like you really want is a way to create a closed-source library. That's a separate request that has come up before...
Yea , an example would be forum accounts pixel library.
All someone would need to do to compile in there source could be this
#include "http://byond.Forum_Account/Pixel_Movement"
And upon getting the Page, compiles the code along with it but the players themselves never have access to "mod"/edit it.