I'm sure they're not going to sue anyone
I'm aware of that, but from a legal standpoint it's a massive risk. Copyright damages for willful infringement are positively massive, and for a smaller company it's essentially a corporate death sentence (and if you haven't correctly set up a corporate veil you're in serious
trouble). There are many people who simply won't take that risk, however small it may be. Because copyright enforcement in the digital setting is patchwork at best, people can and do get away with flying under the radar. Never mistake that for being in the legal clear; when copyright law bites it can be ruinous.
Nandrew's point stands; this guy is on questionable legal grounds if he doesn't have solid licensing for every single third party asset he's using. He probably will never be called on it, but that's a risk he's choosing to take.
I don't know what "please" means in lawyer-speak, though.
Lawyers can spend hours arguing over a single word. This is probably one of those such words, which is to say I wouldn't attribute any particular meaning to it. However, the statement "the fourth line is optional" is probably more important than the word "please". If it was necessary to state that the fourth line is optional, this implies the rest is mandatory, which implies that some rights were reserved.