What are some alternatives?
When comparing DD-WRT and OpenWISP, you can also consider the following products
OpenWrt - OpenWrt is an open-source firmware based on Linux for wireless routers
MikroTik RouterOS - The main product of MikroTik is a Linux-based operating system known as MikroTik RouterOS.
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
Gargoyle - Gargoyle Router Firmware home page
ClearOS - A very good alternative for Windows Server, for free