OpenJDKJRE as replacement for jPortable and launcher java settings

I'm trying to make a a portable version for bancika's DIYLC drawing package relying on a Java runtime available.
I can get it working using the jPortable package and the existence of the commonfiles\java folder.
But the recent licensing issues around Oracle I feel the need to make the switch to the OpenJDKJRE variants.

When I have only that runtime installed (32 or 64) the PortableAppLauncher does not seem to find the package if Java=required is defined in the INI files in the app tree. It does work if I make a copy of it in a Java folder there or rename OpenJDKJRE64 to Java.

How is the use of a specific Java runtime is defined or searched in the Commonfiles ?
I tried to figure out from the source code but I could not figure out where to look