Ubuntu 14.04 / 16.04 (recommended)
Go here to add the opencpu repository. Also have look at the readme for rpm packages.
Debian / CentOS / Suse etc
See the readme on building deb or rpm packages from source.
Docker containers based on various platforms are published via dockerhub:opencpu. Use opencpu/base for opencpu or opencpu/rstudio for opencpu + rstudio server. See this readme for more details.