I don't know much about these things and I'm making this up as we go but I wonder if we can use AGPL or a stronger version of AGPL. Basically, you pay for a subscription or everything on your servers that touches this software must be free and open source. Should work for researchers and students and there is a continued revenue stream. For example, require any software that talks to a rest API also be foss. With more people paying, the subscription can slowly become cheaper and more accessible. Thoughts?
Do you really expect people to pay for something when they can get it for free?
Making software open source means you are either selling something complementary (hardware, other software, services) or else begging for crumbs.