Yep, you can
see here some of the info I was compiling for it when during beta. A lot of that is outdated, there have been further developments and new things, eg toolset works again in Linux with Wine. I meant to update later, but there was still a weekly dev patch at the time so I couldn't keep up
You can't use it to play on Layo, which is not running on EE and is still on version 1.69. I think this is still true:
I'd encourage anyone that wants to support NWN's future to buy EE (it's worth noting that Steam takes a big bite out of that if you get it from there), though obviously if you are only interested in NWN insofar as it involves Layo, don't rush to the bank because I think you'll be alright until further notice
I'm not a big fan of the OC, so if I were someone whose
only interest in NWN was Layo and the OC, I would not buy it or recommend it -- provided I could actually run 1.69, which is of course not true for a lot of people on modern systems. I love NWN though, so I'm happy it was picked up and is being actively developed, again - especially by people pulled from the modding community.