Ok so as someone who has run community challenges for UGC as a Manticore employee at Core Games, I have some big opinions on this. I’m curious what @RayBenefield envisioned when they proposed the idea of jams. Ray, what logistics did you envision? Are you thinking these would be judged, or more informal? What results are we looking for, with this program? I think it’s very important for us to identify the desired result before jumping in. I do agree that if high stakes prizes are involved there would need to be clearly defined rules and rubrics for judging, for fairness. I think lowering the stakes might help.
For me, some goals are to inspire creators to learn UEFN features and skills they might not normally use. And to foster public, well-archived sharing of info and resources among creators. Like Forum posts and Snippets! I like the idea of creators integrating their challenge entries into their existing long term UEFN projects. It could prompt them to add or expand features in their existing projects, or maybe start a new long term project. For that reason I’m not sure about the requirement that entries would need to start from scratch. Also "not from scratch is a very difficult honor-system rule to verify and enforce. For prizing, maybe there’s a way to keep it low stakes. If the goal is inspiring many entries, high stakes prizes like cash can drive quantity but not necessarily quality. Many creators are also motivated by lower stakes “bragging rights” incentives like Forum badges, leaderboards, or, public features, even just likes or upvotes. If you look at Inktober art challenges on Instagram, or at the Wikipedia editor community, none of those creators are winning prizes. They just want to challenge themselves, and to be a part of something big. And there’s also the idea of rewarding participation (aka nobody is a loser, because participating is an achievement in itself.)
The idea of judging and prizes makes me a little nervous, because when I was an employee on the Manticore Creator Relations team (aka CRel, Core Games’ version of Dev Rel), we ran a monthly community “Challenge Board” with prompts and cash prizes for art assets and scripts. The program became a huge toxic mess that we had to shut down after several months of issues, and it entries didn’t even produce much value for the platform. Core’s Challenge Board was a constant ongoing program that became the one of our most visible ways of interfacing with the community. The prizes were hundreds or thousands of dollars. For UEFN, maybe a couple of one-off lower stakes challenges wouldn’t be as risky. I definitely do not recommend what we did at Manticore.
Here are some lessons from Manticore. These may not all apply in UEFN’s case. First, administrating/judging/prizing diverted a lot of employee time away from our other tasks. It also unintentionally pitted CRel employees against creators, where instead of encouraging and inspiring creators we were judging winners and losers (and dealing with the monthly fallout when creators blamed us for results they didn’t like). It encouraged talented creators to bounce around between quick small projects for cash, rather than develop their promising long-term passion projects and teams. Maybe the worst consequence was a toxic effect on Core’s social scene. Monthly cash-earning competitions fostered an adversarial mindset among creators instead of collaborative. Creators were incentivized to choose solo-work over teamwork so they could keep the whole prize instead of splitting it. People started keeping their skills and resources secret from each other.
I do believe creative challenges can inspire great work, and bond communities together. That’s why I wrote this Feedback post requesting them, lol. 
Clearly many game jams are a great example of that. But on the other hand challenges can harm a community if they’re not carried out carefully, so I wanted to share some lessons from my experiences.
I look forward to seeing where this goes!