According to the linked site.
Beyond gaining a better understanding of Islam it is astounding to me how many of the verses from the Qur’an and how many of arguments Muslim theologians and commentaries use sound identical to those used by Calvinists to rationalize the doctrine of predestination. My guess is that if you removed the flowery language and substituted certain words such as Allah in many of the quotes from the Qur’an or Muslim commentaries with the word God that the statements would be indistinguishable from statements on doctrine from not just the Reformers of John Calvin’s day but also indistinguishable from those in modern Reformed Theology like John Piper, R.C. Sproul and others.
I am not sure of the value of this line of argumentation in a critique of Calvinism, however. First, a similarity to something is Islam is not an automatic problem. Muslims do get some things right. Secondly, the Calvinist responses here seem to involve theological voluntarism, which is certainly a natural inference from some things Reformed theologian say, but I don't think is essential to Calvinism. I did say at some points in my exchanges with Calvinists a few months back that I thought that the theodicy moves they were making could as easily be made on behalf of Islam as well as on behalf of Christianity.
The comparisons are interesting in their own right, however.