Can an open source license demand to leave a link to my site

Question

Let's say I want to develop a public website and make it open source.

Can an open source license demand that derivative work keep a link to the original site in a prominent way?

On the one hand this shouldn't look like a problem, as it seems similar to the widespreaad "leave credits clause in source code". On the other hand, source code is not end-user-visible and such a demand to leave a link to the original site in prominent display means I am denying the freedom to modify that particular place of the software that causes the link to be displayed.

NOTE: All answers below have an implicit IANAL disclaimer

UPDATE: The question is not whether such a clause can exist (which I understand it can) but whether the license can still be called open-source with such a term.

Answer 1

This is an attribution clause, which I don't see as a major problem.

Or course, it's difficult to enforce as if they don't follow the attribution clause, it may be hard to know if they're using that software.

Answer 2

Frankly a license is just a contract to use the code. The choice is up to the implementor whether to use your code and it's license or not.

The problem is that you can place anything you want in the license, but unfortunately it's up to you to find and pursue violators of the license, which is the problem with most GNU licenses (except for the FSF's pursuit of Tivo ;) so up to you.

I actually think for a web based API it's a great idea. Problem is that you'll get lost in the noise I think, you'd probably want to say that the user must provide a copyright page which has a clear statement including your URL (I'd personally specify font size and colour as "prominent way" is much to wide a definition)

But as I mentioned, the issue is with the enforcement, not the terms.

Answer 3

The license can demand it. The question is whether that will turn enough people away from using your code.

I would have usability concerns with having a link on my web-page which is targeted at other web-developers rather than my user-base.

Consider demanding the link should appear in comments in the HTML source, rather than on the rendered page.

Answer 4

Your major question depends on your definition of "open source." And just to reiterate, I am not a lawyer.

If by "open source" you mean "anyone can poke around in the source code," then yes, this is fine. The original BSD license had a clause requiring anyone who produced a derivative of the work to include the name of the original work's author/owner with their license. This was known as the "advertising clause," and is now absent from the modern BSD license because the "advertising" grew to around 90+ names and companies in some documented cases.

If by "open source" you mean "GNU-style free software," then probably not. Your license will NOT be compatible with the GNU GPL, which I believe expressly prohibits such advertising clauses.