Hi Olivier,
Unfortunately, there's currently no way to obtain account identifiers at this time. We're currently researching MCC support and will try to make this easier when that happens.
Since scripts are currently tied to the account, one workaround is to define a global variable such as
var ACCOUNT_NAME = 'My Account';
and update that when adding this script to an individual accounts. Then the script body can just refer to ACCOUNT_NAME and will see the value for this account.
- Kevin Winter
AdWords Scripts Team