This depends on the laws of the country in which you reside. Generally speaking, you shouldn’t sign something unless you know exactly what it says and you agree to it. If you don’t speak the local language then you could either get a translator or a lawyer or both.
But in some countries there are protections for people who don’t speak the local language well. For example, in Japan, there’s an expectation that employers, and especially larger employers, will make relevant paperwork available in the employee’s native language. And if they don’t do so, they can end up losing in court, and this has happened many times in the past.
Of course, even if you’re in a country where the law partly backs you, it’s still ideal to confirm things as best you possibly can. You don’t want to get screwed first, and then have to hire a lawyer and go to court. If that happens then that’s what you do, but if you have a better option up front, take it.
Well look. Obviously there are security issues. JavaScript has its own share, PHP has an extra large share. The question has always been when the commercial businesses will decide that they need to fund the open source projects they rely on.