I'm applying math graduate program and know that some program reads "gre math subject is not required". Does that mean I can't send gre subject score to them?
And if I also want to apply cs program, can I send gre math sub score to them to exhibit my mathematical ability?
You can still send it in. You can always add more information to your application, but there is no guarantee that they will consider it. I know a few schools have stopped asking for GRE subject scores because they don't feel that it's a good way to predict performance, and if that is the case they will not look at it. Assuming you have a good score, it will not count against you.
You can and should send them. Not required means it is not essential; they don't want someone who has not taken that exam to worry. But grad schools would typically want to know about a candidate from as many sources as possible and getting your subject GRE scores is really a good plus point for your candidature. Of course , additional fee for each report has to be borne
