When selling server jars through our services, we have policies that you must ensure you're abiding by. Failure to comply will result in a warning just like any other rule violation.
CraftBukkit forks, Spigot forks, Paper forks, and forks of any derivatives must follow the terms set by the GNU GPL, including providing the unobfuscated source code of the distributed project to any buyers who request access, for no additional charge.
All server jars downstream of other projects must provide credit to all relevant sources where code has been utilized from.
Server jars that market themselves as optimised improvements of other projects must include specific benchmarks of how they are better than the program they are being compared to. Descriptions must include proof of the performance improvements with fair benchmarks depicting how the programs compare to each other in order to show that there are genuine improvements to optimization.
The Mojang server software or a substantial copy of it, modified or not, may not be redistributed, in accordance with Mojang's EULA. If you're modifying Mojang's code, it is our recommendation that you redistribute your changes as patches which end users may then apply themselves locally on their machine, likely using tools like paperclip or similar.