It is steadily becoming a lot more open - Jeb's the lead developer now and a big focus has been put on adding mod support. They've hired the guys behind Bukkit (a popular third-party mod manager for servers) to help with that, I believe.
Clones have also started to appear but it's still small indie companies making them, meaning it'll take time before many are at the same level as Minecraft.
However, the bigger companies do seem to be paying attention (an EA bigwig spoke about Minecraft in a Gamasutra piece the other day [1], though he was saying fairly obvious things), so it'll be interesting to see what the genre's like in 5-10 years' time.
Clones have also started to appear but it's still small indie companies making them, meaning it'll take time before many are at the same level as Minecraft.
However, the bigger companies do seem to be paying attention (an EA bigwig spoke about Minecraft in a Gamasutra piece the other day [1], though he was saying fairly obvious things), so it'll be interesting to see what the genre's like in 5-10 years' time.
[1] http://www.gamasutra.com/view/news/167137/Minecrafts_future_...