Praise be to Allah.
There is nothing wrong with setting up a website to provide work for jobseekers and connect them with employers in return for commission paid either by the worker or the business owner, or both of them, according to the terms of the agreement. That comes under the heading of brokerage.
Al-Bukhaari (may Allah have mercy on him) said in his Saheeh: Chapter on the fee of a broker. Ibn Sireen, ‘Ata’, Ibraaheem, and al-Hasan did not see anything wrong with paying a fee to a broker. End quote.
In that regard it is stipulated that the website should limit its activity to facilitating connections for permissible work only. It is not permissible to act as a middleman or agent for doing haraam work, because Allah, may He be exalted, says (interpretation of the meaning): “And cooperate in righteousness and piety, but do not cooperate in sin and transgression. And fear Allah; indeed, Allah is severe in penalty” [al-Maa’idah 5:2].
There is nothing wrong with working for Amazon on the Mechanical Turk website, if the worker is not helping in anything that is haraam.
If we assume that there are haraam jobs that are requested by jobseekers, but his work is far removed from that and he is not helping in that in any way, then his work is permissible.
And Allah knows best.