OpenUI5 now includes the ability to easily run a simple node.js server via grunt, see the following instructions
openui5/developing.md at master · SAP/openui5 · GitHub
I expect the browser security is preventing the direct access to the files, have you tried running with the --allow-file-access-from-files flag in Chrome?
It might be easier to provide a relative path to the resources directory, i.e. if the resources directory is at the same level as the app directory you could do something like :
<script src="../resources/sap-ui-core-all.js"
Regards,
Jason