These projects are so big and complex that even with open-code a malicious actor is sometimes able to insert damaging code. Who suddenly made this decision? Did the US government order them to do this? If the US government can order them to do this, can they order the elevated coding status of a “benevolent” contributor on the US government payroll who is then ordered to put in a very hard to detect exploit? Open code doesn’t mean exploit free, it means exploits are more likely to be patched.
I’ve missed extremely discounted sales for services I like and have been frustrated about it before. It seems fine for protonvpn to do this just once but the should also just add a toggle.