I'd be using an older copy of GameMaker to make my game. The LootLocker extension only supports version 2.3+ of GameMaker which I don't have. Would this be an issue that might disqualify me from making something for the jam or can I still participate?

You need an online leaderboard, only when you want to be top 3. Otherwise you can use an offline one.

I reckon I'll enter then and if my game does well I guess I'll cross that bridge when I come to it. Might be the excuse I need to upgrade to the latest version of GameMaker.

Thanks for getting back to me :)