Thank you for raising this question, it's really important. We have included this question and its answer on our Marketplace FAQ
- all publishers who have at least one published marketplace listing will receive not-for-resale (NFR) licenses for the Sitefinity Small Business Edition, Sitefinity Standard Edition, and Sitefinity Professional Edition. Those NFR licenses can only be used for development of Sitefinity add-ons for the Marketplace.
I hope this information is helpful, Jochem! If you need further assistance, please do not hesitate to get back to us at your convenience!
Grisha 'Greg' Karanikolov
the Telerik team