thanks for the update etienne! just thought you might like to know, the 3.5.0a jupload app hosted on your wiki is corrupt. the zip archive posted here is 416kb, the one on the wiki is ~375kb.
The same for the 3.4 zip file. If I try to unzip on my linux box (ubuntu 8.10) I get a CRC error (inflating: jupload/wjhk.jupload.jar bad CRC d5d13bf2 (should be edc0db4c))
If I upload the zipfile to the same linux box using coppermine plugin manager it looks as if it installs. But the jupload tab doesn't work. Looks like a poor error handling in coppermine (1.4.21)