Replied to Automatically sending Webmentions from a static website by James Mead (jamesmead.org)
I'd also like to find a way to say thank you to Aaron Parecki who built webmention.io and Ryan Barrett, Kyle Mahan, et al who built brid.gy. However, I can't see a way to do either and, indeed, the latter explicitly say "We don't need donations, promise." 
In the past, I’ve heard many of them say to make a donation or support the IndieWeb Open Collective instead.