Praise be to Allah.
It is not permissible to subscribe to the app mentioned, or to work on programming it or to help with it in any way, because it is based on gambling which is haraam. That is because the subscriber pays money in the hope of getting more by clicking on products, and this may or may not happen. Gambling means certain loss and possible gain.
Al-Bujayrimi (may Allah have mercy on him) said: Gambling is something that is done with the possibility of either gaining or losing." (Haashiyat al-Bujayrimi ‘ala Sharh al-Manhaj 4/376).
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: Gambling – which is any transaction in which there is the possibility of either gaining or losing, and the one who is involved in it does not know whether he will be a winner or a loser – is haraam in all cases. In fact it is a major sin, and it is obvious to anyone that it is reprehensible when he sees that Allah, may He be exalted, mentions it alongside idol worship, khamr (intoxicants) and divining arrows." (Fataawa Islamiyyah 4/441).
Moreover, these illusionary transactions that are done to raise the value of the items sold involve deceit and cheating the purchasers, and deceit is haraam; in fact, it is a major sin, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever deceives us is not one of us.” Narrated by Muslim in his Saheeh, no. 101.
Please see also the answer to question no. 406946 .
And Allah knows best.