I know what he's saying but cannot answer his question.
what he's asking is : Is there some way of making a map that has a feature to it that prevents it from being run on a server that isnt running a special pluggin for AMXmod. He wants to "watermark" his map so that only servers with his little pluggin can load the map.
He wants to make it so people can download and play a map if its on his server, but can't run it on thier own servers without his permision via a special "key" pluggin.
Believe it or not I think that might actually be possible by either exploiting an intentionaly made error that the pluggin nullifies, or perhaps make an "Impossible" entity that the pluggin tells the server what data it is missing. A good example of this is to put a model entity with an impossible file path. This will crash the map, and/or HL. Give that entity a specific name that the AMX plugging can itercept on file load from the map data and impose the correct file path.
I can think of a number of ways to do this, but do not have experience with the coding/capabilities of AMX. Beyond that, I'm not sure what to tell you. I would hope that by asking a question like that, you have the know how to do the pluggin yourself.