got it working. you need to reset your PATH and then rehash and launch it as above (example for OSX only):
thibaultkick$ PATH=/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home/bin:$PATH
thibaultkick$ hash -r
thibaultkick$ which java
/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home/bin/java
thibaultkick$ java -version
java version "1.6.0_37"
thibaultkick$ java -Xmx2048m -jar '/Applications/Technic Launcher.app/Contents/Resources/launcher/technic-launcher-latest.jar'
