Prerequisites
Notes
jagexappletviewer.jar from
OldSchool.msi was used because it allows the copyright footer bar to be removed upon logging in
2) 3)

The copyright footer was
not hidden with OpenJDK 12, 13, and presumably any JRE newer than 11 if
jagexappletviewer.jar comes from
OldSchool.msi 4)
Install
sudo dnf install java-11-openjdk wmctrl && sync
sudo apt install openjdk-11-jre wmctrl && sync
Show Java Paths
sudo update-alternatives --config 'java'
Old School RuneScape
rm -Rf ~/'runescape/oldschool' '/tmp/oldschool' && mkdir -p ~/'runescape/oldschool' '/tmp/oldschool' && wget -O '/tmp/oldschool/OldSchool.msi' 'https://www.runescape.com/downloads/oldschool.msi' && 7z e -o'/tmp/oldschool/OldSchool-msi' -y '/tmp/oldschool/OldSchool.msi' && 7z e -o'/tmp/oldschool/rslauncher-cab' -y '/tmp/oldschool/OldSchool-msi/rslauncher.cab' && cp '/tmp/oldschool/rslauncher-cab/JagexAppletViewerJarFile'* ~/'runescape/oldschool/jagexappletviewer.jar' && cp '/tmp/oldschool/rslauncher-cab/JagexAppletViewerPngFile' ~/'runescape/oldschool/jagexappletviewer.png' && rm -Rf '/tmp/oldschool' && sync
Desktop Launcher
Old School RuneScape
Exec='s Java path may need changed depending on the distro
Change uiScale if-needed
mkdir -p ~/'.local/share/applications' && nano ~/'.local/share/applications/Old School RuneScape.desktop'
[Desktop Entry]
Name=Old School RuneScape
Comment=Relive the challenging levelling system and risk-it-all PvP of the biggest retro styled MMO. Play with millions of other players in this piece of online gaming heritage where the community controls the development so the game is truly what you want it to be!
Categories=Game;Java;AdventureGame;RolePlaying
Exec='/usr/lib/jvm/java-11-openjdk-amd64/bin/java' -Xms256M -Xmx2G -XX:+UseConcMarkSweepGC -Duser.home='/home/CHANGEME/runescape/oldschool' -Djava.class.path='/home/CHANGEME/runescape/oldschool/jagexappletviewer.jar' -Dcom.jagex.config='http://oldschool.runescape.com/k=3/l=$(Language:0)/jav_config.ws' -Djdk.tls.client.protocols='TLSv1.3' -Dhttps.protocols='TLSv1.3' -Dsun.java2d.opengl='false' -Dsun.java2d.uiScale='1' 'jagexappletviewer' 'oldschool'
Type=Application
StartupNotify=true
Path=/home/CHANGEME/runescape/oldschool
Icon=/home/CHANGEME/runescape/oldschool/OSRS.icns
StartupWMClass=jagexappletviewer
Actions=Screen;Cache;Notes;
[Desktop Action Screen]
StartupNotify=false
Exec='/usr/bin/wmctrl' -r 'jagexappletviewer.jagexappletviewer' -x -b 'toggle,fullscreen'
Name=Toggle Fullscreen/Windowed
[Desktop Action Cache]
StartupNotify=false
Exec='/bin/bash' -c "rm -Rf '/home/CHANGEME/runescape/oldschool/jagexcache' '/home/CHANGEME/runescape/oldschool/jagexappletviewer.preferences' '/home/CHANGEME/runescape/oldschool/jagex_cl_oldschool_LIVE.dat' '/home/CHANGEME/runescape/oldschool/random.dat' '/home/CHANGEME/runescape/oldschool/'*'.log' '/home/CHANGEME/runescape/oldschool/.java' '/tmp/oldschool' && sync && notify-send 'The Old School RuneScape cache has been cleaned.'"
Name=Cache Cleanup
[Desktop Action Notes]
StartupNotify=false
Exec=gio open 'https://wiki.realmofespionage.xyz/games:old_school_runescape'
Name=Installation Notes
sed -i 's/'CHANGEME'/'$USER'/g' ~/'.local/share/applications/Old School RuneScape.desktop'
Icon
rm -Rf '/tmp/oldschool' && mkdir -p '/tmp/oldschool' && wget -O '/tmp/oldschool/OldSchool.dmg' 'https://www.runescape.com/downloads/OldSchool.dmg' && 7z e -o'/tmp/oldschool/OldSchool-dmg' -y '/tmp/oldschool/OldSchool.dmg' && cp '/tmp/oldschool/OldSchool-dmg/OSRS.icns' ~/'runescape/oldschool/OSRS.icns' && rm -Rf '/tmp/oldschool' && sync
Quick Commands
Clear Cache
rm -Rf ~/'runescape/oldschool/jagexcache' ~/'runescape/oldschool/jagexappletviewer.preferences' ~/'runescape/oldschool/jagex_cl_oldschool_LIVE.dat' ~/'runescape/oldschool/random.dat' '/tmp/oldschool' && sync
Execute
Old School RuneScape
cd ~/'runescape/oldschool' && java -Duser.home='.' -Djava.class.path='jagexappletviewer.jar' -Dcom.jagex.config='http://oldschool.runescape.com/jav_config.ws' -Dhttps.protocols='TLSv1.2' -Dsun.java2d.opengl='false' -Dsun.java2d.uiScale='1' 'jagexappletviewer' 'oldschool'
-XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:+AlwaysPreTouch -Xms'512M' -Xmx'512M' -XX:-UseBiasedLocking -XX:+DisableExplicitGC
-XX:+UseNUMA
File Manager
Root
gio open ~/'runescape/oldschool'
Testing
jagexappletviewer.jar
jagexappletviewer.jar has varying filesizes depending on where it's sourced from, along with different functionality depending on the host operating system
7)
Windows
rm -Rf '/tmp/oldschool' && mkdir -p '/tmp/oldschool' && wget -O '/tmp/oldschool/OldSchool.msi' 'https://www.runescape.com/downloads/oldschool.msi' && 7z e -o'/tmp/oldschool/OldSchool-msi' -y '/tmp/oldschool/OldSchool.msi' && 7z e -o'/tmp/oldschool/rslauncher-cab' -y '/tmp/oldschool/OldSchool-msi/rslauncher.cab' && cp '/tmp/oldschool/rslauncher-cab/JagexAppletViewerJarFile'* ~/'Downloads/windows-jagexappletviewer.jar' && rm -Rf '/tmp/oldschool' && sync
macOS
rm -Rf '/tmp/oldschool' && mkdir -p '/tmp/oldschool' && wget -O '/tmp/oldschool/OldSchool.dmg' 'https://www.runescape.com/downloads/OldSchool.dmg' && 7z e -o'/tmp/oldschool/OldSchool-dmg' -y '/tmp/oldschool/OldSchool.dmg' && cp '/tmp/oldschool/OldSchool-dmg/jagexappletviewer.jar' ~/'Downloads/macos-jagexappletviewer.jar' && rm -Rf '/tmp/oldschool' && sync
Android
am start -n 'com.jagex.oldscape.android/.AndroidLauncher'
am force-stop 'com.jagex.oldscape.android'
Windows
Create Directory
if not exist %UserProfile%"\runescape\oldschool" mkdir %UserProfile%"\runescape\oldschool"
start %UserProfile%"\runescape"
Java
-
Extract the root folder from the archive and drop it in the runescape folder
Folder structure should be %UserProfile%\runescape\jdk-14
javaw.exe should exist at %UserProfile%\runescape\jdk-14\bin\javaw.exe
jagexappletviewer.jar
Batch File
cd "jdk-"*"\bin"
start javaw.exe -Djava.system.class.loader="app.systemclassloader" -Duser.home="..\..\oldschool" -Djava.class.path="..\..\oldschool\jagexappletviewer.jar" -Dcom.jagex.config="http://oldschool.runescape.com/jav_config.ws" -Dhttps.protocols="TLSv1.2" -Xms"768M" -Xmx"768M" -Dsun.java2d.uiScale="1" "jagexappletviewer" "oldschool"
macOS
need macOS dmg .jar
Need OpenJDK 13 or something in the ~/runescape folder
OpenJDK 9 had GPU usage and lower FPS
Need -Djava.system.class.loader=app.systemclassloader

This
very likely needs refactored
rm -Rf ~/'runescape/oldschool' && mkdir -p ~/'runescape/oldschool' && curl 'http://oldschool.runescape.com/downloads/jagexappletviewer.jar' -o ~/'runescape/oldschool/jagexappletviewer.jar' && curl 'https://lh3.googleusercontent.com/WLvp10q8TwtyVgMsYL7gW0c7NVG5vnFcRNS7oQtTnSyWbM9kgo_MS8QZa3bsylNgZDba' -o ~/'runescape/oldschool/jagexappletviewer.png' && sync
#!/usr/bin/env zsh
cd ~/'runescape/oldschool'
~/'runescape/jdk-13.0.1.jdk/Contents/Home/bin/java' -Djava.system.class.loader='app.systemclassloader' -Duser.home='.' -Djava.class.path='jagexappletviewer.jar' -Dcom.jagex.config='http://oldschool.runescape.com/jav_config.ws' -Dhttps.protocols='TLSv1.2' -Xms'768M' -Xmx'768M' -Dsun.java2d.opengl='false' -Dsun.java2d.uiScale='1' 'jagexappletviewer' 'oldschool'
Legacy Java Client
notepad "%UserProfile%\jagexcache\jagexlauncher\oldschool\oldschool.prm"
-Djava.class.path=jagexappletviewer.jar
-Dsun.java2d.opengl=true
-Dsun.java2d.accthreshold=0
-Dcom.jagex.config=http://oldschool116.runescape.com/k=3/l=$(Language:0)/jav_config.ws
-Xmx512m
-Xms256M
-Dhttps.protocols=TLSv1.3
-XX:+UseSerialGC
jagexappletviewer
Jagex Launcher Flags
--disable-gpu --disable-software-rasterizer --single-process --launch=osrs --silent