Hey @Klaus
I'm trying to understand your questions (utilizing the Translation tool, of course). Let me assist you by responding to your queries.
GPL License
With the premium version, you retain the freedom to implement changes as per your requirements for your specific projects or clients. That's cool nature of any OpenSource projects including TYPO3 ;)
Feature Request
We always welcome to our customers to get their wishlist. If you have idea(s) to improve the extension, Feel free to share with us. We will be happy to consider them in upcoming versions.
License Policy
I regret any confusion, there seems to be a misunderstanding. We don't impose charges for usage on domains like DEV, staging, testing, etc. You can easily whitelist those domains to your license key. You don't need to buy a separate license for such domains. I'll ensure the team responds within 24 hours. Just submit a quick ticket at https://t3planet.com/support
Free vs Premium
To your last question, You can readily explore distinctions Free Vs Pro Features
section at https://t3planet.com/typo3-news-comment-extension
If you still have any inquiries, feel free to create a ticket, and we'll be delighted to assist you.
Cheers, Sanjay