Root Certificate
Java <= 1.4 had the problem that the default installation did not support CAcert´s root certificate, due to the strength of the root key.
I was told now that you can solve this problem, by downloading and installing the so called "unrestricted policy file"
http://media.wiley.com/product_data/excerpt/30/07645963/0764596330.pdf
http://mail-archives.apache.org/mod_mbox/gump-general/200403.mbox/<m3znaz4df7.fsf%40bodewig.bost.de>
http://forum.java.sun.com/thread.jspa?threadID=644328&tstart=225
This should make Java 1.4 work with CAcert.
Please send me feedback, whether it works for you or not.