TL;DR if you're planning on releasing something with source code you have to understand the consequences.
As for your example, people get to play your game regardless. At that point it comes down to what you want when making your game. Do you want your name plastered all over something popular? Do you just want to make something people will enjoy? Something else?
Ignoring all the fluff in this sort of debate, it ultimately comes down to whether the creator is A) Making the game for themselves (for the recognition, money, ect), B) Making the game for the love of the art form, or C) Somewhere inbetween.
When money's involved, it's easy to justify closed source because they could be trying to make a living off it. Without money, in non-profit projects such as SMW hacking, that excuse doesn't exist. So, it depends solely on your opinion: Is making games for one's own recognition alright?
If it is fine with you, or if you don't think people's motivations are any of your business, then you still have to understand one thing: Of closed and open source, one helps the community as a whole go forward, the other withholds information and makes people reinvent the wheel on a regular basis.