This is a great resource for datasets for medical imaging with AI and surprisingly complete in the areas that I searched.

A nice complement to the widely usee TCGA datasets

Thanks a lot. This is an amazing website.

Can a dataset be GPL'd?

The specific structure and presentation of it could be, and the items individually could be. There are some jurisdictions where a dataset as such rather than just the structure and presentation have legal protections, but those are slightly distinct from copyright AIUI, and as such I imagine you'd want a tailored license for that rather than GPL. They're called database rights.

The ODbL is a sharealike open license for datasets.

https://opendatacommons.org/licenses/odbl/

As in anything developed using it also becomes GPL?

Yeah