[Quantlib-users] regarding permission

[Mudit S. <sha...@gm...>]

Dear list,

I intend to derive a commercial product relying on Quantlib. I just want to
be sure that
I can use Quantlib freely for my product. I have read the license and I
think my product will not violate it. However I have a doubt :

1)  In this page : https://www.quantlib.org/license.shtml
there it is mentioned :  It allows proprietary extensions to be
commercialized
I wanted to know what exactly is meant by this statement.
Can the extension be anything ? another library/api/website/blog etc ?

Hoping to hear from you soon,
Mudit Sharma