In honor of the spirit of TTRPGs (also because it's good practice and I felt like paying back what I've gotten from the TTRPG community), OIL is now under CC BY-SA 4.0!! What does this mean? It means that you are, to copy from the CC website themselves,

You are free to:
Share — copy and redistribute the material in any medium or format for any purpose, even commercially.
Adapt — remix, transform, and build upon the material for any purpose, even commercially.
The licensor cannot revoke these freedoms as long as you follow the license terms.

ALL you have to do is release your derivative work under the same CC BY-SA 4.0 license and give appropriate credit to whatever you're modifying, along with marking changes and differences!

AS WELL, I've gone through and cleaned up the PDF of OIL, making it a bit easier to read as well as hopefully to print.  

If you haven't checked it out yet, we also have a JAM going on at https://itch.io/jam/splattered-with-oil-jam!! Come join in!