[hilios]

>If I do GPL, I have to make sure that I'm following the rules set out in that license

If its all your own stuff you don't really have to care about the license. Otherwise the rules are pretty simple, include a GPL license and if requested by a user supply the source code (which you can even charge some money for).

>and making sure others who have based their code on my project have done the same.

If you don't care what others do with it, you don't have to enforce it.

As the sole copyright holder (A)GPL only gives you more options.