OpenAlex data is made available under the CC0 license. That means it's in the public domain, and free to use in any way you like. We appreciate attribution where it's convenient, but it's not at all necessary.
There is one exception: the MAG Format snapshot is released under ODC-BY, as per the original MAG license applied by Microsoft (it reuses their schema). See the LICENSE.txt file in the MAG format snapshot distribution for attribution requirement details.