This little elaboration will help you along the way:
http://www.euclideanspace.com/maths/geometry/affine/aroundPoint/index.htm[
^].
It shows how to combine the rotation matrices with a translation to achieve the rotation about a given point. The page you found gives you the rotation matrices for each axis rotation R
0. The article I pointed to gives you the two transform matrices T
-1 and T.
The resulting matrix for the rotation about the point (x,y,z) is then:
R(x,y,z) = T-1 * R0 * T
Alternative notation:
R(x,y,z) = T-1 x R0 x T
Best Regards,