Well other way around free antiviruses is to join beta tests, actively help developers and they might reward you with full license. Thats very common way to get full featured payable antivirus. You have to work a bit but it's probably easier than paying for it. If they don't give the license, you had the chance to freely use their new tool. Of course you already understand the risks and responsibilities of using beta software right? And this way you also create program to your taste if you have cool and useful ideas But go to beta testing only if you're serious about it and bug reporting, not just because you MIGHT get a free license!