procrastinator - MMF2 is not a Construct clone, if anything it would be the other way around. Clickteam has been around long before Scirra and started the style of event editing that both Construct and GameDevelop (and maybe others) use today. I think the Scirra developers used to make extensions for MMF2 also before creating Construct.
GameDevelop has differences like working on linux as deadeye says and as far as i know it is also not even a project fork, it just looks similar to Construct and uses the same event system but is different and i would not describe it as a clone.