No, you can buy as many as you want. There is no limit.
For the free ones, the process is the same but they appear as already paid without going through PayPal.
If they are free, to prevent them from being bought all at once, I have established that you must issue an review of the previous one.
I think that the "reviews" of a plugin issued by users are a great value to the information before buying, downloading, installing and risking wasting time.
Currently there are 71 but there will be many more, every day I upload 2 or 3. I have been uploading the most striking of Purus, but since nobody comments on anything I am going to upload all of Aron with the due warnings ... We all know that they are very dangerous plugins for the stability of OxWall because they are a real botch, but we must admit that they are great, beautiful and have no equivalent. Perhaps having the source code, a developer will be encouraged to remake them.
For the payment plugins I have made it optional to publish a review or not.
I think the plugin you are looking for is "Resend Verification Email" from the author "Johnathon Weaver", which was at https://developers.oxwall.com/store/item/1217
and that it was eliminated by its author. It cost 15 USD and the author described it as "Allows site administrators to re-send verification emails"
In maximum 24 hours you will have it in the store for free, I will remake it and it will not require licenses because it will be free. Now it is very late in my country.