Invision Power Services (IPS) has probably the most up-to-date and advanced forum software currently available.
While they also offer cloud based solutions their support (or lack of) will make anyone want to cry. It gets interesting with their self hosted plan, which could tie in nicely with what DigitalOcean is currently offering (and looking at the line-up you guys are already supporting other known forum software). The LEMP/LAMP setups go nicely with IPS so there's that. Such things and great support on top of that is a rare thing these days, there's a whole market of beginners that lack the knowledge of how to setup a server and it's something to consider as a business.