We contacted Apple’s developer support to find out if app subscription offer codes can be used as crowdfunding rewards.
The answer is simple and clear. “Read the Lisense Agreements.”
Well, it’s as they say. However, the developer program license agreement is over 100 pages long and the text is difficult to understand, making it difficult to read.
Perhaps the additional conditions regarding use of the In-App Purchase API are a point to which particular attention should be paid.
The next thing to check is whether the conditions for being a subscriber can be met and whether it is possible to operate as a subscriber without making any income. Continuing research including implementation methods.