Back in the days TubeX, LinkX and TGPX were three of the most popular adult webmaster tools for running XXX tubes, adult linklist and porn TGPs. All 3 were producted by JMB Soft along with scripts for traffic trading and making toplists
However, JMB Soft closed, left all scripts as public domain/open source and disappeared. That means the scripts are still out there, running on plenty of sites – but never updated. So, they do not support modern versions of PHP and are therefore no longer secure
But. Now there is a revival. Adultlist.com have released TGPX and LinkX in new versions compatible with PHP7x and thus fully secure. TubeX according to their page is just days away from an upgraded release
Best of all, they are all released for free and still open source: