I think @cm-steem has mentioned in the past. Projects do not want to pay GRC to the volunteers because of tax/legal concerns.
Maybe a third-party donation site could work. A one where people can donate any crypto to a project and it automatically gets converted to GRC and rained on the researchers.
I too, would like to see either Gridcoin or a new BOINC coin on Graphene. The more I read about PoS, it seems to be much less secure than PoW of DPoS.
That is a fair concern. The projects could just rain the GRC though, which would probably not classify as paying the crunchers? I am guessing here, and the law would probably be different depending on where in the world this were to happen...