[sandworm101]

>> None of these products claim to be HP.

HP would claim that the simple statement "compatible with HP xyz printer" makes it counterfeit, an improper use of HP trademarks in the statement. HP wants a world where anyone searching for "Ink for HP printer" will only ever see HP-licensed products.

[lokar]

https://en.m.wikipedia.org/wiki/Nominative_use

[sandworm101]

>> The user does nothing to suggest sponsorship or endorsement by the trademark holder.

HP would say that "compatible with HP printers" goes well beyond nominative. Per HP documentation, HP printers are only compatible with HP-licensed ink. So anyone saying "compatible with HP" is incorrectly stating they are licensed by HP.

Try selling a cupholder, or a cup, that is "compatible with Ferrari" and you should expect lawyers. (Ferrari famously hates aftermarket parts.)

[HeatrayEnjoyer]

HP and Ferrari are not the oracles of what can be compatible with their products or not. Compatibility is a physical trait, not something you can license or gatekeep.

[lokar]

Visit your local (American) drugstore. Next to each branded item will be a store brand version with the text “compare to $BRAND”