>makes showcase video in style of free use Sonic engines
>only mentions in a single comment chain that he doesn't intend to let other people use it
>"wow, you guys are so entitled"

On the one hand that's his right to do. On the other hand it is an asshat thing to do. If he like many, many more before him burns out (because he didn't allow community help him by making it open), disappears or otherwise drops the project then all that effort was in vain and community that could've helped him gets nothing. Even on the off chance if he does finish his project, then it would have no future since community that couldve made new levels for it, can't.
And since many of the fan-game makers do exact same thing, exceedingly small amount of them actually get finished, and most of them disappear off the face of the internet.