What are some alternatives?
When comparing OpenWISP and MikroTik RouterOS, you can also consider the following products
LibreMesh - An Open Source Sofware for Geek-free Mesh Community Networks.
pfSense - pfSense is a free and open source firewall and router that also features unified threat management, load balancing, multi WAN, and more
OpenWrt - OpenWrt is an open-source firmware based on Linux for wireless routers
ClearOS - A very good alternative for Windows Server, for free
Gargoyle - Gargoyle Router Firmware home page
IPFire - IPFire is a server distribution with intended to use as a firewall.