I'm building a desktop application and I'm downloading font ".ttf" files from Google Fonts with the application. I've managed to do that by utilizing the JSON response from the Developer ...

A OpenType/TrueType font file should contain a "name" table, which has an array of so-called "Name Records" that provide all kinds of information like font name, version, creator, copyright, license, etc.

Fore example "Open Sans" has (among others) these two Name Records:

nameId: 13 (License Description)
text: "This Font Software is licensed under the SIL Open Font License, Version 1.1. This license is available with a FAQ at: https://scripts.sil.org/OFL"
nameId: 14 (License Info URL)
text: "http://scripts.sil.org/OFL"