Oracle's latest Java 8 still provides the Firefox Java plugin, no need to use an outdated version. There are already enough security risks, especially if used in a workplace. JRE8 was recently tested to install and work in dCore using the dCore-java-installer command, which creates a nice SCE extension and Firefox plugin:
http://wiki.tinycorelinux.net/dcore:dcore-java-installer_commandIt probably wouldn't be too hard to manually create a TCZ instead, or modify the script, pasted below. Just manually download the JRE and follow steps from ~ cd "$UNPACKDIR" onward. Once created i think it was self-contained and didn't require any dependencies.
Oracle's JRE8 can be downloaded here:
http://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.htmljre-8u112-linux-i586.tar.gz
The download contains the precious libnpjp2.so file, but if IIRC during dCore testing the entire JRE needed to be installed, maybe YMMV.
Of course this assumes you're okay using Oracle's software.
dCore-java-installer:
#/bin/sh
# (c) 2014 Jason Williams
# 2016 Java 8 update, help info, end of script notes, UI improvements and more by nitram
#  Based on script by:
#"---------------------------------------------------------------"
#"                Java Installation Script (0.2)"
#"              Created by Mars11 "http.//mars11.com/""
#"---------------------------------------------------------------"
> /tmp/select.ans
. /etc/init.d/tc-functions
if [ "$1" == "-h" ] || [ "$1" == "--help" ]; then
	echo " "
	echo "${YELLOW}dCore-java-installer - Create a JRE 8 SCE (Java Runtime Environment, eg."
	echo "                       jre-8u92-linux-i586.sce).${NORMAL} Imports JRE only, not JDK"
	echo "                       (Java Development Kit), may use option combinations."
	echo " "
	echo "If >1 web browser installed select from list, opens Oracle Java JRE 8 download"
	echo "site, manually download file (eg. jre-8u92-linux-i586.tar.gz) to home"
	echo "(eg. /home/tc/) or /tmp directory, then prompted to create the SCE."
	echo " "
	echo "Re-run this script and repeat the process when Java updates available"
	echo "(eg. Firefox will flag Java plugin out of date)."
	echo " "
	echo "Oracle JRE 8 download site:"
	echo "www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html"
	echo " "
	echo "Usage:"
	echo "${YELLOW}"dCore-java-installer"${NORMAL}     Create a Java SCE."
	echo "${YELLOW}"dCore-java-installer -b"${NORMAL}  Create a Java SCE, add SCE to sceboot.lst."
	echo "${YELLOW}"dCore-java-installer -e"${NORMAL}  Create a Java SCE, search home and /tmp"
	echo "                         directory for an already downloaded jre-8*.tar.gz file."
	echo "${YELLOW}"dCore-java-installer -r"${NORMAL}  Create a Java SCE, create SCE in RAM."
	echo " "
exit 1
fi
echo " "
while getopts rbe OPTION
do
	case ${OPTION} in
		r) RAM=TRUE
		echo "Using the -r option."
		sleep 1
		;;
		b) ONBOOT=TRUE
		echo "Using the -b option."
		sleep 1
		;;
		e) EXISTING=TRUE
		echo "Using the -e option."
		sleep 1
		;;
		*) exit 1 ;;
	esac
done
shift `expr $OPTIND - 1`
NICE=`grep "^NICE=" /etc/sysconfig/sceconfig | cut -f2 -d=`
	if [ -n "$NICE" ]; then
		if [ "$NICE" -gt 19 ]; then
			NICE=19
			echo "Using nice level 19, 19 is the highest possible nice value."
		elif [ 0 -gt "$NICE" ]; then
			NICE=0
			echo "Using nice level "$NICE", only root can use negative nice values."
		else
			echo "Using nice level "$NICE"."
		fi
		sleep 1
		/bb/renice -n "$NICE" -p $$
	fi
echo " "
echo "${YELLOW}dCore-java-installer:${NORMAL}" && sleep 3
echo " "
echo "*  This script imports Oracle's Java Runtime Environment 8." && sleep 3
if [ "$EXISTING" != TRUE ]; then
	echo "*  Ensure Firefox, Iceweasel, Nautilus, Midori or Chromium are loaded,"
	echo "   otherwise see dCore-java-installer --help regarding the -e option." && sleep 3
fi
echo " "
echo -n "Press Enter to proceed: "
read ANS
echo " "
if [ "$EXISTING" != "TRUE" ]; then
	{ which firefox | grep -v ondemand ; which nautilus | grep -v ondemand ; which chromium | grep -v ondemand ; which iceweasel | grep -v ondemand ; which midori | grep -v ondemand; } | sort | uniq | select "Select a web browser to download Java (JRE 8):" "-"
	read BROWSER < /tmp/select.ans
	rm /tmp/select.ans
	if [ "$BROWSER" == "q" ]; then
		echo " "
		echo "Load Firefox, Iceweasel, Nautilus, Midori or Chromium and re-run script,"
		echo "otherwise download jre-8*.tar.gz to home or /tmp with another browser"
		echo "and run 'dCore-java-installer -e' (see dCore-java-installer --help)."
		echo " "
		exit 1
	fi
	echo " "
	echo "*  Opening Oracle Java JRE 8 download page with "$BROWSER"." && sleep 3
	"$BROWSER" http://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html > /dev/null 2>&1 &
	echo "*  Manually download jre-8u**-linux-i586.tar.gz to home (eg. /home/tc) or /tmp." && sleep 3
	echo " "
	read -p 'When downloaded press Enter to import Java Runtime Environment: '
	echo " "
fi
TCEDIR=/etc/sysconfig/tcedir
if [ "$RAM" == "TRUE" ]; then
	UNPACKDIR=/tmp/oracle-java321
	mkdir -p "$UNPACKDIR"
else
	UNPACKDIR="$TCEDIR"/import/oracle-java321
	mkdir -p "$UNPACKDIR"
fi
FILE=`find ~ -name "j??-8u??-linux-i586.tar.gz"`
if [ ! -f "$FILE" ]; then
	FILE=`find /tmp -name "j??-8u??-linux-i586.tar.gz"`
fi
if [ ! -f "$FILE" ]; then
	echo " "
	echo "Java runtime or development release *.tar.gz file not found, exiting.."
	exit 1
fi
FILENAME=`basename "$FILE"`
PKGNAME=`basename "$FILENAME" .tar.gz`
DIRNAME=`dirname "$FILE"`
echo "*  Using $FILE."
sleep 3
echo "*  Copying "$FILE" to:"
echo "   "$TCEDIR"/import/debs/"
sleep 3
cp "$FILE" "$TCEDIR"/import/debs/
echo "*  Creating Java extension:"
sleep 3
echo " "
sudo tar -xvf "$TCEDIR"/import/debs/"$FILENAME" -C "$UNPACKDIR"
cd "$UNPACKDIR"
if [ ! -d usr/lib/jvm/ ]; then
    sudo mkdir -p usr/lib/jvm
fi
if [ ! -d usr/bin ]; then
    sudo mkdir -p usr/bin
fi
if [ ! -d usr/share/applications ]; then
    sudo mkdir -p usr/share/applications
fi
if [ ! -d usr/share/pixmaps ]; then
    sudo mkdir -p usr/share/pixmaps
fi
sudo mv ./j??1.8.?_?? usr/lib/jvm/java1.8
if [ -f usr/lib/jvm/java1.8/bin/java ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/java usr/bin/java
fi
if [ -f usr/lib/jvm/java1.8/bin/javaws ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/javaws usr/bin/javaws
fi
if [ -f usr/lib/jvm/java1.8/bin/jcontrol ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/jcontrol usr/bin/jcontrol
fi
if [ -f usr/lib/jvm/java1.8/bin/jjs ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/jjs usr/bin/jjs
fi
if [ -f usr/lib/jvm/java1.8/bin/keytool ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/keytool usr/bin/keytool
fi
if [ -f usr/lib/jvm/java1.8/bin/orbd ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/orbd usr/bin/orbd
fi
if [ -f usr/lib/jvm/java1.8/bin/pack200 ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/pack200 usr/bin/pack200
fi
if [ -f usr/lib/jvm/java1.8/bin/policytool ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/policytool usr/bin/policytool
fi
if [ -f usr/lib/jvm/java1.8/bin/rmid ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/rmid usr/bin/rmid
fi
if [ -f usr/lib/jvm/java1.8/bin/rmiregistry ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/rmiregistry usr/bin/rmiregistry
fi
if [ -f usr/lib/jvm/java1.8/bin/servertool ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/servertool usr/bin/servertool
fi
if [ -f usr/lib/jvm/java1.8/bin/tnameserve ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/tnameserve usr/bin/tnameserve
fi
if [ -f usr/lib/jvm/java1.8/bin/unpack200 ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/unpack200 usr/bin/unpack200
fi
if [ -f usr/lib/jvm/java1.8/bin/ControlPanel ]; then
	sudo ln -sf /usr/lib/jvm/java1.8/bin/ControlPanel usr/bin/ControlPanel
fi
sudo cp usr/lib/jvm/java1.8/plugin/desktop/sun_java.desktop usr/share/applications/"$PKGNAME".desktop
sudo cp usr/lib/jvm/java1.8/plugin/desktop/sun_java.png usr/share/pixmaps/"$PKGNAME".png
if [ ! -d usr/lib/mozilla/plugins/ ]; then
	sudo mkdir -p usr/lib/mozilla/plugins/
fi
sudo ln -s /usr/lib/jvm/java1.8/lib/i386/libnpjp2.so usr/lib/mozilla/plugins/libnpjp2.so
cd ..
if [ -f "$TCEDIR"/sce/"$PKGNAME".sce ] && busybox mount | grep " /tmp/tcloop/"^$PKGNAME$" " > /dev/null 2>&1; then
	mksquashfs oracle-java321 "$TCEDIR"/sce/update/"$PKGNAME".sce -noappend
	cd "$TCEDIR"/sce/update/
	md5sum "$PKGNAME".sce > "$PKGNAME".sce.md5.txt
	sudo rm -r "$UNPACKDIR"
else
	mksquashfs oracle-java321 "$TCEDIR"/sce/"$PKGNAME".sce -noappend
	cd "$TCEDIR"/sce/
	md5sum "$PKGNAME".sce > "$PKGNAME".sce.md5.txt
	sudo rm -r "$UNPACKDIR"
fi
if [ "$ONBOOT" == "TRUE" ]; then
	if ! grep -wq "^$PKGNAME$" "$TCEDIR"/sceboot.lst; then
		echo "$PKGNAME" >> "$TCEDIR"/sceboot.lst
		#echo "$PKGNAME entered in $TCEDIR/sceboot.lst."
	fi
fi
echo " "
echo "${YELLOW}Imported "$PKGNAME".${NORMAL}" && sleep 3
echo " "
echo "Notes:"
echo " "
if [ "$ONBOOT" == "TRUE" ]; then
	echo "*  $PKGNAME added to $TCEDIR/sceboot.lst."
fi
echo "*  Run sce-load $PKGNAME to load this extension."
echo "*  Manually remove "$FILE" as desired."
echo "*  If old version installed:"
echo "       * Remove old /etc/sysconfig/tcedir/sceboot.lst entry"
echo "       * Reboot system"
echo "*  Firefox Java plugin installed, restart browser to activate."
echo "*  Java plugin test:"
echo "       *  http://java.com/en/ -> Do i have Java?"
echo "       *  http://www.test-java.com/"
echo "*  Import and load bash to launch ControlPanel (or jcontrol)."
echo "*  Default security high so most web applets won't run, at own risk use"
echo "   ControlPanel to add Exception Sites and modify security settings."
echo "*  ControlPanel can also remove temporary files, enable debug console, etc."
echo "*  Re-run this script to install Java updates."
echo " "