Ask them to develop the MVP and app for free as they're bound to become a multi billionaire.
No paperwork of course, you're friends.
It's like making a car 10cm longer. To change the paint we'll spray paint it and you can pick it up tomorrow. If you want to change to leather seats then it’s going to be a few days work come back at the end of the week.
But if you want the car 10cm longer then that’ll cost millions – and, likely take a year to complete.”
"C/C++ are unsafe." Only if you don't know how to manage memory & don't leverage tools.
"javascript doesn't need classes." It's the native language of the web, it better damn well cater to the preferences of the significant propertion of programmers who HAVE to use it.
Generally: "Language X is bad because reason Y." No it isn't. You're using it wrong!
#define while if
#define else
#define free(x) ;
#define assert(x) (x && rand())