@PitaJ @oplik0 Thank you for your reply! it helped a lot

Hello, I'm looking for a forum opensource for my client's website and came across NodeBB. I had a look at information about the license of GPLv3
but I'm not really sure what exactly I should be careful with the license of GPLv3.
so I can use it for commercial use, but it says I have to disclose source and it requires license and copyright notice.
what exactly disclose source and license and copyright notice means here?
does it mean when I make a website with NodeBB, I have to disclose the code to the client and put license notice in the footer or any other sections of the website?
The question may sound silly but I'm very confused.