The wordmark DINplus (for example "DINplus" or "DIN+") may not be used because it constitutes a misuse of a certification mark. The legal basis for this is enshrined in the Trademark Protection Act.
Wordmarks as well as company identifications are protected under §§ 14, 15 of the Trademark Protection Act as the exclusive right of the trademark owner. Trademark law protects the owner's interests via § 14 (2) no. 1-3 of the Trademark Protection Act in various ways.
As well as the protection of identity § 14 (2) no. 2 of the Trademark Protection Act also provides protection against confusion. Trademark protection merely requires that the offending trademarks be identical or similar. Similarity of marks in the trademarks is thus the primary pre-requirement. This includes, for example the use of DINplus or DIN +. Similarity is always deemed to exist if the sound, image or sense of the trademarks should coincide.
The second pre-requirement is that in addition to similarity of signs the goods or services offered by the offending trademarks should be identical or similar.
Finally, the coincidence or identity of the trademarks, which is the third pre-requirement, must result in the risk of confusion. Such is the case if the target group might believe that the goods or services in question originate with the same company or alternatively with companies which have a commercial association with each other.
This state of affairs as regards protection is known as trademark protection, inasmuch as it depends on the degree of similarity which is exhibited by a mark on the one hand, and by the goods or services on the other, and is also influenced by the distinctiveness of the older trademark. The greater the degree of brand awareness or the unique nature of the trademark, the swifter will the risk of confusion arise.