Tinder Sues Dating App 3nder Over Alleged Copyright Infringement

— -- The ever-expanding dating app Tinder has filed a lawsuit against a startup called 3nder over alleged trademark infringement, arguing that the names are similar enough to cause confusion in the market.

Tinder, owned by Match Group (which also holds OKCupid, Match, and other dating businesses), traditionally is used for an individual looking for another individual, while the much smaller 3nder is mostly aimed at people and couples searching for threesomes.

In a December letter to 3nder, Tinder's law firm, RGC Jenkins & Co., threatened to sue the startup in U.K.'s High Court unless it stops using the name 3nder. A Tinder spokesperson confirmed to ABC News today that the company has filed a lawsuit, but declined further comment on the case.

But the startup isn't bowing out quietly.

"Our mission and our values could not be more distinct from those of Tinder. We have and always will put ethics and aesthetics first," 3nder founder Dimo Trifonov said in a statement Monday. "Our members seek something else entirely when they come to us -- to explore their sexual curiosity and date in an open-minded space. With so many sexualities and relationship structures left out of Tinder and the Match Group offerings, there is room for all of us. No one should have a monopoly on love."

Tinder lawyers argue that the name 3nder can lead consumers to the mistaken belief that the app is associated with or sponsored by Tinder, and gives 3nder an unfair advantage, according to legal letters 3nder founder Dimo Trifonov said he received from Tinder.

“It's an unfair fight, first of all. The big guy bullying the little, so classic, just because they can," Trifonov told ABC News today. "At stake is the freedom of passionate people like me."

In response to the legal move, 3nder has launched the social media campaign “Tinder S--- My Socks,” asking supporters to tweet pictures of their socks at the dating app giant.

“As a busy start-up, it is a common occurrence for the 3nder team to forget to do their laundry," Trifonov wrote in a statement as a social media call-to-arms, calling on its members "and anyone with an open-mind" to use social media "to send Tinder their dirty socks.”

Trifonov said the idea to fight Tinder with smelly socks came to him very naturally.

“It was about 2 a.m. when I realized we had no clean socks because of this nonsense lawsuit. So, we decided to use the hashtag as a weapon hoping that people will be compassionate about our human problems," Trifonov told ABC News.

"Startups are a cure to a chronic issues in our world, where conglomerates are after pure profit and control." Trifonov added, "If we win, all the 270 independent dating apps are going to win with us.”