You can also go old school hardcore hardware boxing. The equipment cost will far exceed 20 bucks but you are not reliant on software and are future proof. I am all about convience it is the main reason I box. I want to do what I want when I want. I use paid software for the convience and simplicity.

But if want free good software I second HKN and Jamba. I know some folks use AutoHotKey but I have not looked much into that.