GPL license, how to provide source file?

Hi, I don't understand the term that require 3D artist to provide their files once it is published online.
I must give away the .Blend file if I publish image or animation I made with open-source software?
How do I share the source file if I upload the Blend4web generated html to my website?

Thanks.

Long time answering but I just came across this.
FAQ about source files.

"How do I share the source file?"
Using Git and Bitbucket, you can host your source files for free.

Thanks, I am assisting a company to acquire the pro license.