If you absolutely need nodogsplash_0.9_beta9.9.9-1 (2014) rather than the current version, it is probably easier and almost certainly more secure to port it to OpenWrt v18 (or v19, which is imminent). The current version packaged is 3.2.1, from feeds/routing/nodogsplash/Makefile
Personally, I'd worry about running an ancient version of the kernel, OS, wireless, and captive portal software in what I would guess is a public or commercial setting.
I'm not sure why there is such attraction to Chaos Calmer and a long-obsolete version of nodogsplash. It isn't the first time it has come up. Note, for example, the kernel crashes with someone trying in Help understanding error log in Archer C7 v4 with OpenWrt Chaos Chalmer
Searching on "nodogsplash" will return many threads, as well as some suggestions of what high-volume users select for their hardware.
There are several threads on low- and moderate-priced devices that you might want to look at. Long, but full of opinions is
I have never used ZBT hardware, but it sounds like this user has significant good experience with them
(I have personal and very good experience with GL.iNet hardware, but it appears to be a bit more expensive than the ZBT device.)