A portable install mean you install Skychart on a removable media (USB stick, external disk) and you can plug it to any PC to run the application without any further configuration. The configuration is also written to the removable media so you retrieve your preferred settings on any computer.
The version 3.8 or more recent is required for this process

The example is given here for Windows but you can do almost the same on Linux, in this case use the tar installer for an easy setup.
You can also use the portable version for Windows on Linux/Mac by using Wine. This way you need a single USB stick for any platform.

The commands suppose your removable media is mounted on the drive E: change accordingly if it use another letter.

This description use mostly a command line window for the clarity of the explanation but you can also use the equivalent graphical tool.
To open a command line window use the Start menu → Accessories → Command Prompt

1) Create a new folder on your removable media:

E:
mkdir portable_skychart
cd \portable_skychart
mkdir Ciel

2) Download the Skychart Windows zip from the Download page. Save the zip file in the folder E:\portable_skychart\Ciel\.

3) Extract the zip file in this folder:

cd \portable_skychart\Ciel
unzip skychart-3.8-2450-windows.zip 

4) Create a folder for the program configuration:

cd \portable_skychart
mkdir userdata

5) Create a startup script:

cd \portable_skychart
notepad skychart.cmd

Copy the following lines and save the file:

@ECHO off
set basedir=%CD%
start %basedir%\Ciel\skychart.exe --config="%basedir%\userdata\skychart.ini" --userdir="%basedir%\userdata"
   

Now you can plug this USB stick on any (Windows) computer and run the program with a double click on skychart.cmd.

If you not want to let any trace in the registry of the computer you need to inactivate the server functionality. Otherwise a registry key indicating the connection port is created.

cd userdata
notepad skychart.ini

Locate the line starting with AutostartServer, set the following and save the file:

[main]
AutostartServer=0

Since the version 3.8 it is possible to copy the configuration file skychart.ini from an existing installation to the userdata folder.

Another option is to save and reload a chart using the menu File/Save as , File/Open.

Mount the configured USB key on your Linux system.

cd /media/my-usb-key/portable_skychart
vi skychart.sh

Copy the following lines and save the file:

#!/bin/bash
wine cmd /C skychart.cmd
   

As you cannot set the executable bit on a FAT file system do the following to run:

cd /media/my-usb-key/portable_skychart
bash skychart.sh