If the people wants to change a job during thier 485 is pending, then they can use this EAD for working with new employer and AP for traveling abroad.
In your case, you want to do a s/w job using H1 and part time job using EAD. But the problem is you are being adjucated by INS for your s/w skills not the part time job. Even if your part time job involves a similar job mentioned in the labor filing, still you will lose your H1 status.
Before your final aprroval has come for 485, say you lost the job or say you wnat a better job, then the need of EAD arises.