So just add the extras-devel repository, add scummvm via the N900 app manager, and then disable the extras-devel.

Don't try to install in CLI a package that doesn't require extra modifications or special installation. Moreover it will left files in your filesystem that won't be deleted unless you clean them manually.

And for information, if a dpkg -i fails because of dependencies, try with a "apt-get -f install", it will solve the dependencies and install your package