So, now there is a version of the Oracle Java that works on RaspberryPi! I tried the NetHomeServer on the Pi with the new JVM and I get page loading times under a second in the WEB GUI. The real time analysis of audio input for signal reception takes around 10% of the CPU time, which is acceptable. This means that RaspberryPi is now a practical alternative as platform for NetHomeServer!
There is an excellent description on how to install the Oracle Java version on SavageHomeAutomation.