For use on the web you'll need a server license, though, which is $3800 for one machine. Fine if it's a business with revenue, but pretty steep for side projects or free services.
(There's also a free version for non-commercial users, but it's really only usable for evaluation, because it adds a PrinceXML logo to the generated PDFs.)
We offer our database publishing software as open source (http://speedata.github.io/publisher/index.html). It is used in many commercial environments as a better alternative to XSL-FO. Our software allows much more flexible layouts. That said: english documentation is still behind and we are lacking nice show cases. If you need more info, just contact me.
(There's also a free version for non-commercial users, but it's really only usable for evaluation, because it adds a PrinceXML logo to the generated PDFs.)