MIT-BIH is here. https://physionet.org/physiobank/database/mitdb/
I found a page about licenses, but I did not know about commercial availability of learned models.
license description is here. https://physionet.org/faq.shtml#license see "What are the license terms?" I quote the relevant part about the data license.
There is nothing analogous to the GPL for data, but we permit copying and redistribution of unaltered data from this site without restrictions, in the spirit of the GPL. We do not allow distribution of altered data except under conditions that make it clear that the data have been altered, because it is very important that users should be able to distinguish between original data from this site and modified versions of those data.
Thank you very much if you tell me. And I am very sorry if it was not an appropriate question here.
After I posted this question, I found a kaggle page that also distributes the same data. https://www.kaggle.com/mondejar/mitbih-database On that page, the license is CC0: Public Domain. Can I trust this license although the kaggle page is not original ? If so, I think I can use the weights of models freely.