Everyone can join, and the public can vote on who goes into the rocket. Somehow I doubt that that'll result in a good working crew, like what would happen if you actually did a study about it.
On a side note, they're sending 4 people crews. Which means that if you want a safe flight, you need at least 2 qualified surgeons on each flight. (You need a backup, if the doctor gets sick. It's rather hard to operate yourself.)
On another note, they're supplying a nonsufficient Mars base, with no option to dismantle and return. What happens if they run out of funds halfway through?((
According to international Space law, the Netherlands would be responsible to get everyone back. ))
Also, reality shows thrive on conflict between characters. They always choose people with conflicting personality traits, otherwise there's no show.
The whole thing is clearly just a money grab. They ask for an application fee from the participant, they will use the funds to make a shitty reality show about choosing the "astronauts" and then the project will die for some reason already mentioned. The founder is still going to make a pretty buck though.
Technically, it's a nonprofit organization. But yeah, they've a program, but none of the technology they plan to use has been developed yet. For one, they plan to do a really fast transit (230 days), but don't say how.
However, they are the majority owner of the television company that's going to broadcast the reality stuff.