@sebabahn I think that could help you. Try to find the string and get the result... https://www.mql5.com/en/docs/strings/stringfind
search for "[is_license_valid] =>". Something like this:
StringFind(
YOURstring, // string in which search is made
"[is_license_valid] =>", // what you want to find
0 // from what position search starts
);
... and then you can use a StringSubstr to extract the result. Not so elegant but, considering the mql language limitations...
StringSubstr(
YOURstring, // string
start_pos, // position to start with from your code above (StringFind)
length=-1 // length of extracted string considering "[is_license_valid] =>" length
);