is there anyway to take the splash screen of the newton start-up, or is it mandatory if you use it in you game?

no, it's not mandatory. but it's mandatory to give credits! see the license.txt on the official newton download page.

edit out the c-script code which displays the splash screen. i think the splash screen bitmap has to stay in your directory though since the current plugin still checks if it is there.

you can also change that check, just let it make check an own bitmap.
but i think it is nice to give them credits... i also guess it is just fine if you put the splash somewhere in ur credits list.