Sorry for the lack of reply, but the answer is indeed "no". There is no way that I am aware of that can stop anyone from opening a folder and snagging any addons they darned well want. Of course, if said addons are binarized the snaggers will need specialized tools to be able to edit them, but that's true for ANY addon out there. Don't worry, the community won't condone any "stealing" of addons. Likewise, if you for instance release all the addons necessary compiled into one single .pbo (say... "dachevsrpgcollection.pbo"), and state in the readme the addons in there are not for redistribution, then that pretty much solves it.
Still won't stop people from using the stuff outside of your mission, or creating their own missions with them, or playing in the editor with them etc. etc. etc. As it should be when creating stuff. If someone is releasing an addon to the world, then someone should be prepared for the fact that addon will be used.
Wolfrug out.