For clarity's sake.
A "hack," in terms of forum software and most web-based software like communities, is a Modification to the software that provides features not originally put into the software.
Implementing the "Arcade" feature is usually considered a "Hack."
Hacking most web-based software usually deals with adding and in some cases removing code that allows more function-ability by either adding features or taking away features one doesn't find useful.
I don't believe anyone meant in a malicious manner. The terms "hack" and "hacking" are seen by most as purely malicious attempts by idiots to destroy software, but in the world of programming it's has a broader meaning.
As far as if it could be done, yes it can. And php wasn't neccisarly developed by 'hackers' per se. It's also not that difficult to learn as if you know C/C++, it makes it even easier to learn.
Implenting small changes is also pretty easy as there are tons of "hacks/mods" available for most popular board software.
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