(Cross posted from the Mark Jaquith post)
If the plug-in is so great and terrific – and many are – then the dev should have the confidence in their product that the user would choose to list the credit by checking “Yes-Display” in the admin section. Otherwise, it is a forced tax.

Forcing a blog to display an advertisement (credit) is a means of extracting payment from the helpless blog owner. Thus, the plug-in is not actually free because the advertisement/credit is required as the payment (and is sometimes left there even when the plug-in is removed).

The dev who does this seeks to tax the blog owner by forcing the advertisement. Some blogs (not mine) can charge serious money for an advertisement. Uncontrolled credits/advertisements create a revenue leak from the blog.

Should the blog owner invoice the dev for the SEO value of the link and current advertising rates?

If a plug-in developer forces the user to display a credit/advertisement, because the user does not know how to remove it, then that credit is a form of payment and the plug-in is not free.

It could all be handled nicely if the dev had the confidence and integrity to start with a default “no” for display with an easy way to make it “yes” if the blog owner so chose.

Btw: nothing wrong with Socialism if you think sick people, children, elderly, unemployed, should receive healthcare based on their illness and not on their ability to pay. Life has value, even someone else’s.
Semper Pax, Dr. Z