UNAUTH TKOF - THE FLC DID NOT CONTACT DEP CTL FOR RELEASE BEFORE TKOF.

Narrative

AS WE APCHED THE RWY; THE CAPT GAVE ME THE AIRPLANE AND TOOK THE RADIOS. AFTER COMPLETING THE RWY CHKS; HE WAS ON THE RADIOS; RADIOS WERE OFF ON MY SIDE. SUPPLEMENTAL INFO FROM ACN 301542: FO RECEIVED IFR CLRNC ON GND AT DNV WHILE I COMPLETED THE MANIFEST. THE CLRNC INCLUDED INSTRUCTIONS TO HOLD FOR RELEASE AND CONTACT CHAMPAIGN WHEN WE WERE AT THE RWY AND READY. I TAXIED THE ACFT TO THE DEP RWY; ACCOMPLISHING THE REQUIRED CHKLISTS WITH THE FO. WHEN ALL CHKLISTS WERE COMPLETED; I ASKED THE FO IF HE WAS READY TO GO; AND HIS ANSWER WAS YES. I RELEASED THE ACFT TO HIM FOR TKOF AND TOOK OVER COMS; ADVISING AREA TFC ON THE CTAF OF OUR DEP. JUST N OF DNV; I CONTACTED CHAMPAIGN DEP TO CHK-IN OFF OF DNV. AT THIS TIME; I WAS INFORMED BY ATC THAT WE HAD NOT BEEN RELEASED OFF OF DNV. THE CTLR ISSUED AN IFR CLRNC AND WE PROCEEDED ON THE FLT AS NORMAL. WHEN REVIEWING THE CLRNC AS PART OF OUR BEFORE TKOF CHKLIST; THE FO DID NOT INDICATE; NOR DID I INQUIRE ABOUT A HOLD FOR RELEASE RESTR. AFTER COMPLETING THE RWY CHKLIST WHILE HOLDING SHORT; I SWITCHED OVER TO CTAF AND MADE A XMISSION OF OUR INTENTIONS. THE FO ASSUMED I WAS CONTACTING ATC FOR A RELEASE. I ASSUMED WE WERE RELEASED IFR FROM DNV.