Yes. All products including the add-ons are multi-site compatible.
Each site in a multisite setup will require a separate license key. You can selectively turn on/off workflows on specific sites in a multi-site setup.
For example, out of 10 sites in a multi-site setup, you want editorial workflows to be active on 8 sites. On the other 2 sites, you want to continue using out of the box WordPress publishing process. With Oasis Workflow multisite setup, you can activate workflows only for certain sites and create site specific editorial review process.