Using the application without Java installed

[routeconverter]

So if I read your answer correctly I just have to replace/rename the .jar file to have the "most actual" (Prerelease) RC portable  app.

That's correct. And the reason why I've been reluctant with these portable apps: RouteConverter was always designed as a standalone program, which "only" needs Java installed. The advantage of the PortableApps for RouteConverter is that it doesn't store data in the Windows Registry but in the file Data\settings\RouteConverter.reg (if you knew [HKEY_CURRENT_USER\Software\JavaSoft\Prefs\slash\common\io] "application/Directory"="%USERPROFILE%\.routeconverter")

Anyway, here's a new PortableApps version from the latest prerelease:
https://www.routeconverter.com/prereleases/en