On the surface, it's not particularly onerous to ask a user to provide a link back to the person(s) who developed a theme or Web application. WordPress Diva, for example, is providing some nice-looking themes, and is only asking for a link back to theme's Web page and to another site promoting furniture. They're tiny, unobtrusive links at the bottom of the page, well out of the way. Why would this be a bad thing?
For a couple of reasons. One, in this case the license terms are ambiguous when it comes to redistribution. What happens if I modify the theme and want to redistribute it? Is that allowed so long as I maintain the links? Can I add even more links? The linkware license is silent on that point.
But my real concern is what happens when the inevitable link rot sets in. Some users have taken issue with the inclusion of an advertising link, but my concern is that the links will eventually point to something other than what the author originally intended.
Let me provide a small example. I've been helping to promote the Ohio LinuxFest this year, and one of the things I've been doing as a part of that is contacting Linux User Groups (LUG) in and around Columbus, Ohio, to try to spread the word and encourage LUG members to make the trip for the show.
In working off of a list of LUGs that the show used last year, I've noticed that a few of the LUGs have gone inactive and allowed registrations on their domains to lapse -- meaning that the domains now belong to squatters. Going to a domain that used to belong to a LUG now takes you to an annoying page full of ads. (I'm not including links to examples for obvious reasons.)
I note that another restriction on the use of the WordPress Diva themes is "you agree not to use or display these themes on any website that supports or promotes pornographic, illegal, or hate related information." However, should the owner of wordpressdiva.com allow the domain registration to lapse, it's entirely possible that the domain would be snapped up by someone looking to advertise porn sites or something equally objectionable. At the very least, you can almost count on a domain squatter putting up a ad portal on the site.
If that happens, the squatter will benefit from the additional Google juice of all the domains using the linkware theme pointing to the squatter's page in order to comply with the license terms. Those using the linkware themes will have to choose between ignoring the original license terms, linking to a squatter page, or finding another theme. If you've put some additional time and effort into customizing a theme to suit a popular blog, that might be a bit of a pickle.
How linkware could work
Link requirements aren't an insurmountable problem, so long as the author takes a few additional steps to clarify the terms of a linkware license.
One, the license should spell out the terms for redistribution, and if it's allowed. What if I want to redistribute the theme with modifications, plus a couple of additional links? Most linkware licenses are silent on this point, and it should be addressed.
Two, the license should be included with the theme or application itself. I noticed when I downloaded the Skewed Rainbow theme from WordPress Diva's site that there's a license notice on the page where it's available, but no license file included with the theme itself. Including nothing but a URL to the license with the theme assumes that the author's site will always remain as it is now, with the license always available at that URL, which I think we can agree is not a safe assumption.
Finally, the author should specify what happens if the domains that are linked to change hands, or if the content at that URL is unavailable. I'd be hesitant to use a theme with the provision of always providing a link to a specific URL when the domain could wind up in the hands of a domain squatter. I'd also like to know where to find a replacement URL if the original disappears.
The linkware license should include a provision that allows the end user to stop linking to a specific URL if the domain in question changes hands. For that matter, authors might want to include a fallback URL just in case their site design changes and the old URL no longer works.
Unless a license addresses all of these issues, I'm reluctant to use any theme or Web-based software that requires linkware.