Kdenlive is an open source video editor that I use when making videos. Its pretty good and stable, but its not included in the slackbuilds as a complete download so you have to piece the libraries together. All the individual parts can be found via google or slackbuilds.org.
This archive works for me on a 32bit Slackware 14/14.1.
Install everything EXCEPT mlt and kdenlive. THEN install mlt and ensure all dependencies are fulfilled. Once you install mlt clean, then install kdenlive.
Any questions let me know.
Here is a complete archive. Last one were just source tarballs. These are complete packages that can be installed with pkgtool