It had better be really old Java code. This decompiler supports only through Java 8. We're on Java 24 now.
Amazon still supporting Java 8
Not for clients with a commercial license, and there are many.
For us, the biggest driver for getting off Java 8 was SpringBoot dropping support for anything older than 17.
But organizations still using Java 8 will most likely use some kind of Java Enterprise application server with vendor support. IBM will support Websphere with Java 8 until at least 2030 and maybe longer if customers keep paying. I'd guess Oracle has a similar policy.