Kevin Burton doesn't have enough money for server(s). So, for fund raising, he is offering you the privilege of testing his product, if you pay $20.
I think this has a few major problems, that whole paying for servers idea. First off, you can't buy that many severs, unless lots of people pay you $20. Second, if your service needs so many servers now before it is public, I think you should rethink your service. If you can't launch a service on a few machines or even a single machine, I have little faith in your service scaling out.
Since I want to see if anyone is crazy enough to pay for a beta, I am offering an AMAZING DEAL. Buy me things off my Amazon wish list, and I will give you the privilege of testing Apache HTTPD 2.1.8-BETA. If enough people buy me stuff, I might think about working on a 2.1.9-BETA. Look at my list, you don't even need to spend $20 like some of the competing betas. And when this is all over, you will even get the source code.