The middle ground is "source available", although that usually means source made available by the copyright holder under terms that don't meet the Open Source/Free Software definitions. I think just "leaked source" is the best terminology here.
I see, never heard of that term. Still wish there was a term that encompassed all software that has publically available source code. I thought "open source" was it. The literal meaning of the term aligns so beautifully with it.