Yes , it is ethical to use the knowledge that you have learnt while working for your employer and to use this programming knowledge to start your own home base programming business . The reason behind this is while working for your employer you have learnt only such things that required for their business . So ultimately you were serving your employer even by learning new technologies like different programming languages while developing the project for the organisation .
The only thing that you should care about it that you are not disturbing your employer and your office work doesn’t effected by this business . Because in various companies when you join they have an agreement with you that you cant accept others offer simultaneously working with them and many more things .
I have explained each question with reason . Hope you like it .
That’s why you have to read those terms and conditions and work accordingly . Because many people open their own start up in the similar way without leaving full time job and working on our own idea .
Secondly , Yes this will obviously matter if you are working for same client of your employer and of your own business also . If you work like that then so much xhances is that your employer can file a complaint against you for misusing confidential data of the company . So it’s better do not provide services to the same client of your osm business.
See you should not use the data or information that you have collected from your regular job for the shake of your own business . Because you have signed the agreement and accepted the term and conditions in which the organisation clearly mentioned that they will charge you legally if you will misused it . So it’s better you use your expertise without disturbing the clients of the previous or your current employer .
Thus , we can say that it’s better to learn and implement various things without disturbing the previous employer and their clients.