Hi Ferry,
Since your question is about using beans in LotusScript, I assume you're talking about a "traditional" Notes client application, not XPiNC. Have you considered using that? Maintaining the application would probably be a whole lot easier.
Anyway, you're beans are written in Java class files that you've probably created in a src folder somewhere in the nsf. From what I know, these cannot be accessed/ called from LotusScript. The only way to use the same classes in LotusScript I known of is to copy the contents to a Java script library. Since beans are "just" normal Java classes, you should then be able them using LS2J. Not an ideal solution, but it works.
Mark