Kdenlive and MLT can compile and run under Mac OS X. Packages are available from the MacPorts project.
MacPorts is a source-based system — there is not a binary app bundle for Kdenlive. Therefore, Kdenlive and all of its numerous dependencies, including multimedia libraries, KDE, and Qt, must be compiled. This can take a long time and much disk space! Furthermore, it is not unusual for something not to build correctly; it is definitely not something for the novice, impatient, or "faint of heart."
For more details see this.