Who funds his research? If he is funding it out of his own pocket then yes, I think it would be fair for him to have some joint ownership of the IP. However, if it was funded by someone else (e.g. the public) then my view is that everyone who contributed to funding that research should have the ability to access and use the results.
The funding provides the raw materials and the equipment in addition to the grad students' salary, so it is not unreasonable for the funding agency to require some open access to the outcome of the project. But this has to be said in advance, so people can decide whether to live on a low salary for many years while doing highly qualified work. If you want full access to my findings, so I would not be accumulating intellectual capital during my grad student years, then I would like a decent salary.
If you show those results to "the public", they'll likely want their money back. I know I do.