Clarify and streamline Distributions.md (e.g. about Java) (#165)

Author: pierre-haessig

src/docs/getting-started/Distributions.md

@@ -1,26 +1,36 @@
 
-Freeplane is available for differents Operating Systems. All Freeplane setup files are available for [download here](https://sourceforge.net/projects/freeplane/files/freeplane%20stable).
+Freeplane is available for different Operating Systems. All Freeplane setup files are available for [download here](https://sourceforge.net/projects/freeplane/files/freeplane%20stable).
 
 Please find below recommendations to choose which **file to download before installing Freeplane on your computer**.
 
 <!-- toc -->
 
+# Java runtime requirement
+
+Freeplane requires a Java runtime:
+- some of the distributions below embed Java, so nothing else is needed,
+- but the other distributions require **Java to be installed independently**.
+
+When using an independently installed Java runtime, it needs to be of a compatible version number (see details for each distribution). The version to be used by Freeplane can be configured using the [FREEPLANE_JAVA_HOME](Command-line_options_and_configuration.md#select-java-installation-used-to-run-freeplane) environment variable.
+
 # Distributions for Microsoft Windows
 
 * **Freeplane-Setup-with-Java-xxx.exe**: Windows installer with embedded Java.
-* **Freeplane-Setup-xxx.exe**: Windows installer which requires Java 8 to 22 to be installed independently. To use this version set environment variable path  [FREEPLANE_JAVA_HOME](Command-line_options_and_configuration.md#select-java-installation-used-to-run-freeplane).
+* **Freeplane-Setup-xxx.exe**: Windows installer which requires Java 8 to 22 to be installed.
 * **FreeplanePortable-xxx.paf.exe**: runs on Windows using [Portable Apps](https://portableapps.com/) launcher.
 Requires [Open JDK JRE64 portable java version 15](https://sourceforge.net/projects/portableapps/files/OpenJDK%20JRE%20Portable/OpenJDKJRE64_15.0.2_Build_7.paf.exe/download) to be installed on your portable app device. It saves user configuration files on the same device.
-* **freeplane_bin-xxx.zip**: archive without installer. It requires Java 11 to 17 to be installed. To use this version set environment variable path [FREEPLANE_JAVA_HOME](Command-line_options_and_configuration.md#select-java-installation-used-to-run-freeplane).
+* **freeplane_bin-xxx.zip**: archive without installer. It requires Java 11 to 21 to be installed.
 
 # Distributions for Apple macOS
 
-* **Freeplane-xxx-intel.dmg**: distribution with embedded java for macOS with intel or m1 processor.  This distribution includes adaptive Look and Feel VAqua.
-* **Freeplane-xxx-apple.dmg**: distribution with embedded java for macOS with m1 processor. This distribution does not include adaptive Look and Feel VAqua.
+* **Freeplane-xxx-intel.dmg**: distribution with embedded Java for macOS with an Intel or Apple M1/M2/... processor
+* **Freeplane-xxx-apple.dmg**: distribution with embedded Java for macOS with an Apple M1/M2/... processor.
+
+Those distributions do not include the adaptive Look and Feel VAqua.
 
 # Distributions for Linux
 
 * **freeplane_xxx~upstream-1_all.deb**: Debian installer compliant with differents Linux derivatives.
 * **freeplane_bin-xxx.zip**: archive without installer. 
 
-They both requires Java 11 to 17 to be installed. To use them, set environment variable path [FREEPLANE_JAVA_HOME](Command-line_options_and_configuration.md#select-java-installation-used-to-run-freeplane).
+They both require Java 11 to 21 to be installed.