My understanding of it is that 100,000+ are in reserve for existing companies / sites already registered. All you have to do is contact them to let them know, with proof, that you want ownership of yours. After launch there will be a "sunrise" period where if you register with ICANN, and then provide proof to handshake, they will give you ownership. I'm not sure how long that period lasts, I'm guessing for a long time until they feel ICANN is no longer relevant if I had to guess.

The goal of the project seems admirable. Potentially, this can help fund open source initiatives which are sorely underfunded while solving the "how do we find a domain in a decentralized way and verify its trust" issue that currently exists. I suppose time will tell, though.