JDK 7 is End-of-Life. You need a support account in order to download it. You should really be using JDK 8.

Java 5 has passed its sell-by date on October 30, 2009. That means that support is only available as paid business support, which of course requires registration.

You shouldn't really be using Java 5 anymore, unless you're committed to some large, complex installation, in which case you should seriously consider that paid business support - I guess the automatic registration page is intended to drive home that point.

Edit: You can still download Java 5 without registering via the technology archive. (Not any more, it also requires login now.)

From Java 9 onwards, Oracle no longer provides a JRE-only installation kit, either with the Oracle Java badge or the OpenJDK badge. That's why you can't find Java 15 JRE downloads on the Oracle and OpenJDK download sites.

You / they have three options:

1. They can download and install a JDK for Java 15. You or he will also need to deal with the JavaFX JAR and other 3rd-party JARs that your application uses.
2. You can use jlink (or similar) to turn your JAR file into an executable with an embedded (cut down) JRE. You then ship that executable rather than the JAR file.
3. You can recommend that they obtain Java from a 3rd party Java vendor that provides a JRE option for Java 15.

My program contains VM options so that can I embed them within the .jar file?

I don't think you can do that. But it should be a simple matter to write a shell script or batch file which calls (for example) java with the required options.

If you use jlink you can embed JVM options in the executable; see How to set VM options for JLink launcher executable.

The jpackage tool may also be an option, though this is not a production feature until Java 16.