It seemed interesting back then but it's kind of dead since the core developers (Avi Kivity, Nadav Har'El and others) have moved on to another startup called ScyllaDB that is a re-implementation of Apache Cassandra in C++.

The OSv project is indeed now moving much slower than it used to when we had an entire startup company devoted to it, but is not dead - it still has three committers from three companies - myself (Nadav Har'El), Waldek Kozaczuk and Timmons Player. It still works, and you are welcome to try it. OSv is not as minimal as includeOS, which of course depending on your viewpoint and use case, is either a pro or a con. OSv supports more types of hypervisors, and has support for a larger subset of the Linux ABI, can run pre-compiled, unmodified, Linux shared libraries, and supports multi-core VMs.

OSv is a much friendlier entree to unikernals which makes it much more productive for most existing code. Glad to hear development is continuing.