From the looks of things, you could make and submit anything, but to be able to include it in the next Zium, it would have to fit the given criteria. Agreed, if someone had that in mind, it would have been good to know up front. If you still want to add it to the jam, I believe you still can while it's open. By the way, looks good.
Re-reading the page now it makes a lot more sense. Last night when trying to submit an entry I was very tired and easily confused and my brain lit up in panic when I saw the words "must [...] have been made in Unity". It probably would have been more clear to me what was being said if I had read the jam page more carefully in the first place. Sorry for making a fuss and thank you very much for extending the deadline as I had gone to bed without making the submission before seeing your response!