I came to the comments first to answer "what's the catch?". There were no comments at the time so I went to the website. This line near the top seems particularly fair and believable.
> Own your own PAAS. Infrastructure at a fraction of the cost. Powered by Docker, you can install Dokku on any hardware. Use it on inexpensive cloud providers. Use the extra cash to buy a pony or feed kittens. You'll save tens of dollars a year on your dog photo sharing website.
> Own your own PAAS. Infrastructure at a fraction of the cost. Powered by Docker, you can install Dokku on any hardware. Use it on inexpensive cloud providers. Use the extra cash to buy a pony or feed kittens. You'll save tens of dollars a year on your dog photo sharing website.