— we are currently developing the platform and aim to open it to partner game developers soon, then the cooperation is based on revenue share from ads (interstitial ads at the moment, rewarded video coming soon)
while the platform seems very interesting the lack of details might hold back serious developers that have to consider daily costs to run their studios. I think a more precise information, especially done before the start of the jam, would have helped you in get more interest on it. Still there's time and people can join it if you share those details within a couple of days.
Talking for myself for example, I would really like to have spent one month in develop something customised for your platform, but it means that I have to cut on other projects, where, I am aware about the risks and costs. I might still give it a go making something small in one day, but it would be more for curiosity to test the platform more than a serious effort.
My personal case, but I am sure it will be the same for any other professional developer, would be a loss of chance for you and for the developers as well. That's why, once again, my suggestion is to make clear the revenues, at least from the ads. Then privately, you might have some other form of agreement too, but people are always happy to know why they are investing time on making a game that will give to you an income, and maybe, one day, something to the developers (that might still not be enough to cover even the development costs).
Sorry if my post seems a bit too harsh, but I love when people comes out with new ideas and opportunities, so I wish that everyone can benefit from that, rather than lose the chance