Thank you for asking! :) I've just added the following paragraph to the rules section:
"Submitting your game to multiple jams will be tolerated, as long it complies with all the rules of both this and the other jam(s). We reserve the right to disqualify submissions that overdo it in this regard (e.g. submit to 5+ different jams).
When in doubt, please get in contact with us before submitting your game."