The other key limitation here is that trademarks are only protected for their use in trade. If a website called "zfs.example" was used to discuss examples of the use of ZFS, but did not charge, and was not selling or promoting the sale of any goods or services, then it is not an infringement because that is not what a trademark protects against.
I am basing this largely on my knowledge of US law, but I understand that on this point trademark law is generally similar in all countries. Of course, i am not a lawyer, and this is not to be taken as legal advice.
EDIT:
According to the Wikipedia article,
Infringement may occur when one party, the "infringer", uses a trademark which is identical or confusingly similar to a trademark owned by another party, in relation to products or services which are identical or similar to the products or services which the registration covers.
According to Harvard's Overview of Trademark Law
If a party owns the rights to a particular trademark, that party can sue subsequent parties for trademark infringement. 15 U.S.C. §§ 1114, 1125. The standard is "likelihood of confusion." To be more specific, the use of a trademark in connection with the sale of a good constitutes infringement if it is likely to cause consumer confusion as to the source of those goods or as to the sponsorship or approval of such goods. In deciding whether consumers are likely to be confused, the courts will typically look to a number of factors, including: (1) the strength of the mark; (2) the proximity of the goods; (3) the similarity of the marks; (4) evidence of actual confusion; (5) the similarity of marketing channels used; (6) the degree of caution exercised by the typical purchaser; (7) the defendant's intent. Polaroid Corp. v. Polarad Elect. Corp., 287 F.2d 492 (2d Cir.), cert. denied, 368 U.S. 820 (1961).
So, for example, the use of an identical mark on the same product would clearly constitute infringement. If I manufacture and sell computers using the mark "Apple," my use of that mark will likely cause confusion among consumers, since they may be misled into thinking that the computers are made by Apple Computer, Inc. Using a very similar mark on the same product may also give rise to a claim of infringement, if the marks are close enough in sound, appearance, or meaning so as to cause confusion. So, for example, "Applet" computers may be off-limits; perhaps also "Apricot." On the other end of the spectrum, using the same term on a completely unrelated product will not likely give rise to an infringement claim. Thus, Apple Computer and Apple Records can peacefully co-exist, since consumers are not likely to think that the computers are being made by the record company, or vice versa.
I am not a lawyer. But from the above, and from other sources, I take it that the use of of a trademark by someone not the owner to refer to or describe or discuss the trademarked goods (or services), without offering those or similar goods for sale mis not a use "in trade" and therefore is not an infringement, even if the publication contains advertisements for other, unrelated, goods or services.
For example, If I want to post a web page with a course nof instruction about how to use the MS-Windows API, and I use the trademark "MS-Windows" and perhaps other trademarks to identify windows, and if I make it clear that I am not the creator or owner of Windows, then even if the page also contains ads, say for vacation homes, my use of the trademarks is not "use in trade" and so is not an infringement.
