Since August 2016, Airwindos has been funded entirely by donations via Patreon. One of the very few plugin makers that strives to serve the customers, without trying to squeeze every penny out of them. There are no meters on the plugins so you definitely would need to use your ears to make decisions on adjustments.
One of their plugins ,ADClip7, is an incredibly transparent loudness maximizer with three output modes to choose from. Console4 emulation plugin package for your DAW without tone shaping which provides more internal space. Busscolors4 closely emulates consoles. PurestDrive is a virtually transparent clipper.
Read more about these plugins here: https://reaperblog.net/2017/11/4_airwindows_plugins/