That ends in a workaround like the one in Rhino 5 splash screen is annoying . But there may be situations where one wants the splash screen.
A (un)checkable option in Rhino’s GUI would be the best:
Rhino Options:
[X] Show Splash Screen
__ [ ] Always On Top
Or an Extended Rhino Option:
Name / Value
RhinoOptions.General.ShowSplashScreen True
RhinoOptions.General.SplashScreenAlwaysOnTop False
The latter should be possible with some dozens of lines of code, I guess.