It's not just open source projects. I have a project that I am considering converting to open source but have not done that yet so it is still proprietary. It reached a point where it was ready for beta test so I created an open beta. It attracted a few customers and one wanted to buy a license. I thought a yearly license of $250 sounded fair and they agreed to pay it. But then I got to thinking about all the hassle to keep track of that and file taxes. It's just not worth it for just a few customers.

I told them to continue using it for free until it can attract at least 100 customers. Then it might be worth the hassle.