I question is to develop a app like YouTube... It may contain haram as well as halal content... My primary goal is to not develop app like Amazon prime...where only entertainment and haram contents are available... But my goal is to develop a YouTube client that's it... It contains Islam contents; education contents, many useful things too... But it has entertainment too... Will I get punished when someone sees entertainment content from that client app.....
in your question scenario, You know this that it will contain entertainment(music & songs) content..
In one word It’s Haram
If you think it this way, You will find the answer
In general sense , if someone mix beer with water , will it be halal ?
And do not mix the truth with falsehood or conceal the truth while you know [it]. Al-Baqara 2 : 42
Truth is the sign of good deeds and False is the sing of bad deeds ...
You can read this verse also
Allah does not impose blame upon you for what is unintentional in your oaths, but He imposes blame upon you for what your hearts have earned. And Allah is Forgiving and Forbearing.