In 2000, alongside fellow CTM 2015 performer Sharif Sehnaoui, Kerbaj founded the MILL association and associated Irtijal Festival, the longest-running festival for non-conformist contemporary music in Lebanon. Billing esteemed artists from throughout the region alongside contemporaries from the European circuit such as Gert-Jan Prins, Sam Shackleton, Miles Whittaker, and Rabih Beaini's Upperground Orchestra and Morphosis projects, Irtijal is widely regarded as the most prominent assembly for experimental music in the Arab world.

As a trumpet player, Kerbaj has collaborated and performed with a number of respected artists, among them French-Lebanese saxophonist Christine Sehnaoui, the Ariha Brass Quarter with Axel Dörner, percussionist Sven-Åke Johansson and Mats Gustafsson. His Al Maslakh label was established in 2005 as the first experimental outlet the country, and a second imprint, Johnny Kafta's Kid's Menu, was created in 2009 following a collaboration with Lebanese punk-rock outfit Scrambled Eggs.

Kerbaj is the author of numerous books, and his comics and short stories have been published in anthologies, newspapers and magazines in Lebanon, Europe and the States. His visual works have been shown in both solo and group exhibitions in Lebanon, France, England, Spain, Sweden, Germany, Switzerland, Australia, Dubai, Malaysia and the US. He currently lives and works in Beirut.