SlackEX is based on Slackware 14.1. Slackware is the first widely-used Linux system, which is still developing. Slackware has existed since 1993.
New features in version 151211 of SlackEX
I have replaced kernel 4.1.1-x86_64-exton with kernel 4.3.1-x86_64-exton with support for “everything”. KDE is downgraded to version 4.10.5 from version 4.11.1. All other component software is also upgraded to the latest Slackware version by now. I may mention in particular GParted 0.24.0 (latest, not in Slackware’s repositories), VirtualBox 5.0.10 (latest, not in Slackware’s repositories), Google Chrome 46.0.2490.86 (latest, not in Slackware’s repositories), AbiWord 2.8.6 (not in Slackware’s repositories), Gimp 2.8.10 (installed from source), GSlapt 0.5.3h, Firefox 31.7, Thunderbird 31.6, Samba 3.6.8 and GCC 4.8.2. Furthermore I have installed Grub2, which can be used as boot loader (if you want) after a hard drive install. Study the full package LIST.
Slackware is grossly underestimated (in my opinion). This article give you ten (10) reasons to choose Slackware.