Uhhh I'm not sure. I do always play with Optifine. The severs I'm in and play on have some mods?? Like both have the head mod, one has a mod that makes the day going by a bit different. I think that's the only mods they have though??
Nope! According to the JAM's group, you can offer:
Shout outs or social promotion
Digital exchange of trade or skill such as graphic design, fan art, coding, etc
Free creative compilation, trans-formative work or promotional material of their entr(ies)
??? Have fun without crossing the lines below.
People often offer to feature/shoutout the winning entries on their profiles or give a free skin/art request as a prize. Less common now that JAMs are a thing though.