About complete integration
EasyPHPCal by itself is the calendar, the files that allow mambo to place it correctly is a "module"
What your asking for is a "component" I've spent hours going through the tutorials to creating a basic component, and basically it said hello world you just wasted 5 hours
If you've ever taken a look at Brian's code, you would understand that a complete and full integration of this calendar into mambo would take someone, quite awhile. If brian took the time to learn mambo, I'm sure even at that point it would still take some time. As for paying $25/30 for this, I wouldnt even waste my time doing so. If mambo continues the way it has, maybe someone, myself, or Brian will take the time for this project. Until then, I recommend this.
Using version 6 create identical user/pass for other calendar author. Create a news event on frontpage that only that specific user see's, with a link to the administration.
Otherwise, them typing in a simple link address is worth countless hours of someone doing it for them.
By no means is a component out of the picture, its just not within this scope.