I know that, but the labels [ beginner, intermediate or advanced ] are organization specific.
Some organizations add these labels while others not. Unfortunately, there is no channel for this project apart from the GitHub to communicate.
For easy issues, you can directly email to OpenMCT, NASA team. They are very helpful.
This is very true that the more you know the better you do. But, when I started with Open Source for the first time with Angular, I was learning and applying that for the first time.
I will suggest you pick up some easy bugs and cover your knowledge gap for them.
Glad you liked it !!
I am not aware of the acknowledgements for the contributors, but if you want to checkout all the projects of NASA which are open source. You can check that out here https://code.nasa.gov/#/
Many of them are quite active and may have monthly releases.