You can use EAD to work part time for some petty cash while keep original fulltime job for your H1b sponsored employer. Your H1b will be staying valid.
Be careful that this is a gray area of law. Different lawyer may have different opinions. Thus, you never got an official answer from CIS untill they publish a new memo. More likely you won't have problem as you still commit to H1 sponsor.
___________
If an H-1 or L-1 nonimmigrant or H-4 or L-2 dependent family member obtains an EAD based on their application for adjustment of status but does not use it to obtain employment, is the alien still maintaining his/her nonimmigrant status?
Yes. The fact that an H or L nonimmigrant is grantedan EAD does not cause the alien to violate his/her nonimmigrant status. There may be legitimate reasons for an H or L nonimmigrant to apply for an EAD on the basis of a pending application for adjustment of status. [However, an H-1 or L-1 nonimmigrant will violate his/her nonimmigrant status if s/he uses the EAD to leave the employer listed on the approved I-129 petition and engage in employment for a separate employer.]