Good point. Bear in mind that as long as all contributions come from you, you can both release a GPL branch and have another proprietary branch with custom code

Good point. Bear in mind that as long as all contributions come from you, you can both release a GPL branch and have another proprietary branch with custom code you don't want to make public. This does create a problem though: if you are accepting outside contributions to the GPL version, you can't incorporate these into the proprietary version without having the contributors sign an agreement which allows you to do so.