You are right. I have not disclosed that sort of information. My goal with this advert was to "pitch the game" to people, and when interested people reply they get a more ample scope of the project and the team.
Most projects do talk about that, and I myself have in the past when posting for other projects and/or positions, but not having that info laid out allows me to ascertain what sort of people I'm dealing with when they contact us, if they have had experience with these sorts of project, if they understand what components a team has, etc.
I don't believe that not being registered is synonymous of what you said. I would consider the "hobbyist" headline a stronger indicative that people are expected to work in a consistent manner, so that deadlines and schedules can be made and reached, but in a comfortable manner that allows team members to balance their own personal work and their involvement in the team.
Lastly, I completely agree with you (and we've experienced that). It's hard to have people working to the beat of the drum if they have more pressing things to work on, or if they don't feel that driven to compromise so much of their own time, but then again - that varies from person to person. We, as a team - and under these conditions, can only work if people all have the same level of motivation, are driven and professional. Motivation may fluctuate and vary throughout the project, and i think that's a bit unavoidable, but I believe that as a team (and specially if you're leading the team and/or managing it) it should be your aim to always help keep morale up by producing quality content. I believe that ends up being your "stick".