The purchase is to remove ads, but the ads are not too intrusive and respectable. I barely notice them to be honest. I plan to wait for a few more clients to come out and pay a one time fee to the one I like the most. The paid clients are just much more polished than the FOSS ones. I'm very happy the FOSS ones exist, they're like a public option and provide a baseline of quality the paid apps need to surpass, but I'm absolutely happy to have good devs get paid for high quality work. I'm a dev too, I contribute to FOSS, but I sure would like to continue to make a living, so I'd be a hypocrite if I refused to see small devs get paid.