Like I said, you can program extensions to it but within limits. So I don't think you can change the network protocols but you can tweak the walking and combat systems to your liking.

In the future they will provide modules, like physics, economy, combat, that should plug into the system. Not sure yet how that will work but sounds promising.

Oh, and I would keep an eye on it but I wouldn't really consider doing anything commercial with it for at least another 6 months so it has enough time to shake down the software.