Henson has most recently been linked with a move to Wasps but Johnson thinks that if he does play rugby in the near future it should be in the black and purple of the Ospreys shirt after they gave him leeway to deal with off-field matters.
"It's a two-party agreement and nobody put a gun to anybody's head to sign," Johnson said.
"In Gavin's case he should honour his part of that deal too and I'll be encouraging the Ospreys to do that.
"We respected his privacy and gave him what he needed the time off he asked from the game, he needed time off from the game.
"He was a contracted employer and we made a commitment to him that we'd wait and allow him to do that and I've yet to have another conversation with the lad.
"The Ospreys in this case have been really fair and we've got to be fair across the board to what we stand for as an organisation.
"I can't speak on behalf of the board, I can only speak on behalf of rugby in the fact of the message that we're sending young kids.
"You agree to sign a contract, your employers have been nothing but careful with you, respectful of you and showed plenty of courtesy toward you. A contract is both ways.
"If you sign the contract you honour it and that's the way I view it, and I view life that way."