These apps may be used for Halaal or Haram purposes. So, by developing such apps, will one be guilty of helping in sin. The apps will not bring any benefit, not even income, to the developer but may make him known for his works.
You can't control of what others will do with those apps. Therefore you won't be accountable for the sins others will make with your product.
Rest assured with the help of Allah.
And He says (interpretation of the meaning):
“And those who do not bear witness to falsehood, and if they pass by some evil play or evil talk, they pass by it with dignity”
source :https://islamqa.info/en/96662 (last citation, down in the text)