A lot of scripts that are encrypted probably contain stuff that is available unencrypted elsewhere now. I know that a lot of the stuff in my encrypted scripts was new at the time but subsequently alternatives have been made available unencrypted. For instance the class 67 loco I created has an encrypted script but pretty much all its capabilities are now available on other things in clear text scripts, some of them mine.
I keep my libraries encrypted for the reason Andi highlighted, to avoid accidental modification. My payware scripts are all encrypted as they contain an anti piracy mechanism and stuff I'm not prepared to share (yet).
As Lost_Soul suggests, contacting the script author will invariably get you the information you seek. Most script writers are very open to sharing knowledge and helping. I have never had anyone ignore a request and in fact it's usually the opposite, scripters tend to freely offer up ideas often unprompted.
Cheers
Dave