As the spell-checker files are external resources, we can not rely on the applet caching mechanism to cache them, so we had to devise a custom caching mechanism as follows:

First of all, edit-on Pro will check if a spell-checker JAR was already cached on the client. If there is no JAR file, it will download it from the server and cache it on the format "language.xxx.jar" where "xxx" is the value of the "version" attribute of the "spellingchecker" element in the "config.xml". If a JAR is already present on the client, the editor will compare its version against the version specified in the "config.xml". If both versions are identical or the version on the client is more recent, the JAR is not downloaded again. If the version number in the "config.xml" is higher, the new JAR file is downloaded and cached on the client.

So, you only have to increase the number of the "version" attribute of the "spellingchecker" element in the "config.xml" each time a word is added to the spell-checker.