Andrew, you understood and answered my questions perfectly, thank you.

You cannot be paid for your time and effort without agreeing beforehand that the customer will pay for that.

But I need to create a product before I can sell it. In fact, every product is created in hopes of recouping the costs only after it has gone on sale.

Or are you saying that my time spent working on a GPL plugin doesn’t qualify as work for which I can charge (indirectly) by applying a price to the resulting product? Does it even matter if I am charging for my work or for hosting the API?

I am trying to figure out a way to generate revenue from WordPress plugins or themes which doesn’t limit the access to the product and at the same time gives reason to pay for it. Here is what I have come up with, so far:

1. Release a plugin and charge users $10 for downloading it.
2. Make the source code available freely through an SVN repository, so that those who know how to use it and are most likely to improve or help fix it can use it for free.
3. Charge $5 for any update that adds new features while bug fix and security releases are free for everyone.

If someone decides to fork the plugin and upload it to the WordPress repository everytime there is a new update, they are free to do it and I wouldn’t mind. I would still remain the trustworthy source of the original.

This way the whole community could enjoy the continued development of the plugin while the contributing users would receive certain percentage of the revenue generated by that particular update.

I don’t see any downside of this approach.

p.s. I am no thinking about ways have maximum profits. I am only looking for alternatives to the donation model.