JWildfire is open source software, so anyone is free to copy it and make their own version as long as the licensing conditions (specifically the GNU Lesser General Public License) are followed. You can find the source (and fork your own copy if you want) at https://github.com/thargor6/JWildfire.
Jesus contributes his modifications back to the main repository so they can be included in the next official version. So think of his version as a “preview” of the next version. Once Andreas releases a new version, his new variations will be included so there will be no need to use his custom version.
If you are a coder and want to contribute, I’ve written an article on how to do so: https://fractalformulas.wordpress.com/jwildfire-development/. (If you aren’t a coder the article will probably be confusing so ignore it.)