Its development stopped in 2016:

"As of April 15th 2016 I won't be working on this plugin anymore. If someone wants to pick up development feel free to email me. There are some other up-to-date APIs that you may want to check (yowsup, ChatAPI, etc)."*

It has some forks. last commit of tukss' fork says:

"This version and User-Agent makes the plugin work. This switches from Android to S40. The exact version numbers were taken from recommendations in yowsup."*

And jasuarez's fork has a RPM package file (SPEC).

With the help of these, I built and installed the plugin on Fedora. But I couldn't check whether it worked because I couldn't find a way to get my WhatsApp password. Also I tried to compile it for Mer but there is a missing dep: FreeImage-devel.*