Thanks for your interest in LibSourcey! As the maintainer I can say the library is still under active development. There are a number of startups that currently use it in their proprietary code - and maybe some open source code too - so it will continue to be developed and will always remain open source.
Since it was open sourced in '14 it hasn't gained a huge amount of open source adoption, probably since it was never advertised there are already some great alternatives such as boost, but hopefully the power of modern stl and libuv will attract more developers over time.
I'll personally be happy to answer any questions regarding LibSourcey.