He pm'd four out of five of my players...three of us on the same pm. I message him back saying that I'd hardly call my game 'former', and given he's approached four of my writers I felt a poaching coming on. I then invited him to read my game, telling him he owed me that much, seeing as he was trying to steal my players. I kept it light hearted and used lots of smiles, but i think my message was quite clear. Hopefully he'll get the hint.
In my opinion, this is pretty much poaching, if not something very close to it. Especially if he's got the stones to try and falsely advertise your game as finishing up. Let's compare two separate examples:
Lily, if your group game consisted of 15+ players, having someone approach a couple of them because of specific/similar roles wouldn't be a real problem. The game would be big enough to sustain itself (I'm assuming), and this person might just be looking for adept players for certain roles.
However, in your situation, they're going after what seems to be your entire game. Now, I'm not talking about specific people in general, but I've encountered players who simply can't budget their time. They may think they can take on another game, but what ultimately ends up happening is they drop a couple of other games because their attention is suddenly occupied by this new and shiny idea. So they very well could kill the entire game by doing this.
Furthermore, the concept on whether they are justified in running a similar game depends on a couple of things. If it's a very popular franchise (like say in a comic series or tv series), then overlap is inevitable. But if the idea is unique, original, and generated on this site alone, then it's blatant copying, and that's not okay, especially
if they are trying to goad players in your game into theirs.
So, I'd guess I say that what they are doing isn't okay, and definitely warrants a PM to a staff member. I'm running a hentai based group game at the moment, and I'd be super pissed if someone PMed all my players with 'Hey, I see that you are in this type of game, but I don't think it looks very fun. Would you mind joining my similar game with a character similar to yours?' Of course, I have no issue with my players discovering a similar game themselves and expressing their interest to play. That's their decision. But someone just can't go and poach players from one game to their own. That's what interest checks are for. If you post an idea, and people want to play it, they will.
If people don't want to play it, they won't. I've put out a couple of game ideas that generated little to no interest. It sucks, but that's just the way it goes.