You have to take always the matching modules version. This is why the sourceforge archive contains both, a tar file of the main naviserver release and a tar file of the matching modues. install-ns.sh contains always the newest release. NaviServer 4.99.12 is not released yet.
Btw, starting with NaviServer 4.99.12, nsssl will be integrated with NaviServer (no separate module), which allows a tighter integration. For example, ns_http will accept http and https urls, there will be an improved crypto support, etc. The release of NaviServer 4.99.12 should happen during summer.