I'm building a downloadable digital web product for sale. I want to use an open-source third-party library for my product.
This third-party library has two licenses available:
I've three scenarios to consider:
First scenario: If I include this library in my product with GPL license, my product must also be released under GPL (which I don't want).
Second scenario: If I use 'commercial' license of this library, I can release my product under whatever license I want.
Third scenario: My product needs this third-party library to extend its capabilities but it does not necessarily need to be bundled with my product source code. I can program my product in such a way that when a customer installs my product, it'll ask the user to install that third-party resource afterward separately (from some open-source GitHub repository).
This third-party library installation procedure would automatically be done via my product after user confirmation. It will be installed in a separate folder from where my proprietary code is located and my product will then interact with that third-party library via its API.
Question: In the third scenario, do I still need to buy a 'commercial' license, despite the fact that third-party library is not included in source code of my product?