RedHat's ubi8 image can be used without subscription, is freely redistributable, and can be used commercially, according to their FAQ.

Section on subscription:

15. Do I need a subscription to use UBI?

No. The Red Hat Universal Base Images and all associated content can be used for development and deployment without the need for a Red Hat subscription. However, for a fully supported operational experience and access to an expanded list of non-UBI tools, containers built on UBI must be deployed on a Red Hat platform such as OpenShift or Red Hat Enterprise Linux.

Accessing non-UBI content does require a Red Hat subscription.

They do recommend a subscription for operational support.

I recommend reviewing their EULA. Which also states:

With the exception of the Red Hat trademark identified in Section 2 below, each software component is governed by a license that permits you to run, copy, modify, and redistribute (subject to certain obligations in some cases) the software components.