Can I use M-Turbo for multiple domains?

the license is per-site (Magento installation) regardless number of domains that are pointing to it.
If you have multiple domains pointing to a single Magento site, you are fine with 1 license. In such case, specify the "primary" domain that you use to access the site backend.

If you have multiple domains and each of them is a separate Magento installation, then you should have a separate license for each of the sites.