Seems to be the main source (as you’d imagine). From About:
> Is the site a hobby or a business?
> Seat61.com is a personal website, started as a hobby. It's grown and grown, and became my full time occupation in September 2007. However, I'm not a company or a travel agency, just an individual with knowledge that others might find useful. All the information on the site is provided free of charge to users, to help people make journeys by train or ship instead of flying, affordably, comfortably and safely. The site generates income through affiliate schemes, and this supports the site, helps fund my travel habit (...er, I mean research, of course) and buys me the occasional bottle of my favourite Chateau Musar...
edit: And to add, I love the site! I've used to plan many trips to and between France, Spain, Estonia, Sweden and Denmark.