Sync has ads, unless you do a one time purchase, I don’t think I paid for boost but I could be wrong, either way, I have no issue supporting developers. Just because something is paid doesn’t mean it’s inherently bad, if they’re making a living making these apps and they are dedicated to making them better and better I have no issue contributing financially. They are the best two apps. It’s a one time purchase, not a subscription. You can continuously support if you like but it’s not mandatory. And yes they’re closed source, which isn’t ideal but I understand the want to protect their code if it’s their livelihood and they’ve put so much effort into them.