This is my example Pumpkin MC plugin. It has the basic boilerplate you need for any plugin. I will (hopefully) update it when a new breaking version of pumpkin's api comes out. Hopefully. This current version was tested against 432f092, though it should work for at least a little bit.
Currently licensed under the GPL 3.0 since the pumpkin api is technically licensed under the GPL 3.0. I'm not a lawyer, but I believe this means any pumpkin plugins are technically supposed to be GPL 3.0 which sort of destroys the idea of paying money for a plugin since you get the source with it and can share it. Fun fact, this also applies to Paper and Spigot, but I haven't seen an example of this tried in court. Could be interesting. I will re-license this project if the api becomes MIT or similar, but I also don't currently plan on enforcing the GPL.
Tldr: Licensed under the GPL, using this could introduce legal issues, hoping to switch to MIT