How would you partake in the jam? What are your interests in game development. Are you a programmer, level designer, asset creator, music composer? These are all things that fall under basic game development. If you don't know how to code I can point you to resources that can help you HERE.
That doesn't mean you can't partake. You could probably still work with someone and create their art or audio assets if that's your inclination or help with ideas and such for the jam. But if you want to be a developer as in designing or coding a game then you have to use Unity.
Hope this explains everything clearly