Thanks for playing, glad you liked it!
After java 1.8 patch 221, Oracle requires developers purchase a license for commercial uses. Even though games here are often free (non-commercial), it can be easier/safer to avoid the whole situation by sticking to 1.8. Later versions of java should be able to execute 1.8 jars with no problem, so in theory this shouldn't impact the end user, but that said java can be fickle/annoying for the end user anyway - the exe wrap is by far the most popular download.