In TurboTax Online, you should be able to leave the fields blank for the driver's license number, and still e-file your tax returns.
Your driver's license number is actually not required to file your federal taxes, nor is it required to file your State tax return in most states.
Two states, Illinois and Alabama, do require a driver's license to file a state return.
For additional information, you can view the IRS information on New Security Safeguards.