Am I allowed to submit my game to multiple game jams running at the same time? There's another game jam (the Summer Slow Jam: Narrative jam hosted by PIGSquad) running within about the same timeframe as this one, so I was wondering if it's chill with the organisers that I submit my game to both this jam and the other one as well. 

Yes, submitting to other jams is totally fine!  

In fact, it’s welcome as it spreads OGA artwork into other jams!  :)

Just be sure your entry follows the rules of this jam.