First I read your terms of service. It takes a minute to read. There is not hard to understand lawyer speak it is clear and straight forward no hidden "if you use our program you shall owe us your first born child" language.
Second I love that it is just a one time purchase. The reason I like this is because I screwed up a couple years back. I was needing to do something and found a site that could do it and it had a limited free to try but the free didn't do exactly what I needed so it offered a very cheap like $3 use of the program and at no point informed me of the terms of the website or suggest anything other then the $3 payment for a month access. Well I used it to help a girlfriend of the time out and then forgot I even used it. I have hundreds of purchases a month on my credit card and don't always scrutinize my statement and at the time had a lot on my plate and did not notice the site was charging me something like $50 a month. I did not realize for about 3 months that it was charging me. I used the site literally one time. I felt like I was robbed. So you offering a 1 time payment makes this program very appealing.
I hope you do well. I hope you don't ever get greedy and try and milk the users who initially supported you. Good luck.