The game is completely Free-to-Play, with everything being accessible, though there is an item shop for cosmetic (wings for you character) and XP-boost items (X% increases in XP gain), in addition to a donation system to support server costs. Though for copyright reasons the PokéMMO download only provides the tools for client-server communication, but you still need to load in a Pokémon FireRed ROM to actually play (and there's an option to cross-load the SoulSilver/HeartGold ROMs to add extra vanity features, such as having your pokémon follow you around). Detailed instructinos are on the download page.
Trailer and download links are on their website: http://pokemmo.eu/
I hope to see you guys in-game soon, I've made my lair in Channel 2, so make sure to swing by when you have the chance (my in-game name is Aranti, btw). And maybe we'll even duel! (though I suggest you train your pokémon a bit first
*in-game currency, gained from battling NPCs, no real-money payments needed.
note: because almost everything happens server-side and they're more-or-less running on donations, they're trying to keep server load as small as possible, this means that stuff like friend/team requests do not get stored, so you can only send a friend request to a person who is both online and on the same channel as you are. Your friends/team gets stored, don't worry about that, but it can make it tricky to add someone.