Yes, Multivendor is supported in Open Source Shuup.
Although this would mean that you would need to host it independently, and likely you will need a Python/Django developer to set it up for you. You would also need to customize the front for your multishop/marketplace purposes.
We do offer hourly based design and development development services to our customers, depending on your needs.
We also offer Shuup Independent Licenses and support starting at $1250/month.
Read more about Multi-Vendor Pricing and Licensing.
Please let us know if you are interested in hearing more about our development and partnership opportunities.