[jordigh]

He also needs to have registered it in the first place. Trademarks are not automatic like copyright is.

I didn't try very hard, but I couldn't find a "curl" trademark here for software:

http://tmsearch.uspto.gov/bin/gate.exe?f=tess&state=4808:iz1...

[nerdponx]

Sort of. The USA you can claim trademark rights without a registered trademark; that's the difference between ™ and ®.

But the law follows "use it or lose it" rules. If you don't defend your trademark, then in the eyes of the court it is no longer a trademark.

[pferde]

Hold on, that's "defend it or lose it". Author of libcurl clearly is using the name, there are new releases coming out quite often.

[nerdponx]

My wording was unclear, yes. If you aren't defending it, you aren't using it as a trademark.

Think of the term literally; if it's not exclusive to you, it's not longer a "mark" of your specific "trade". It's just a "mark".

[pferde]

Fair enough.

[M2Ys4U]

>He also needs to have registered it in the first place.

Not true. Unregistered marks can still be defended (it's just harder).

That's why there's both ™ and ® symbols. Trademark and Registered Trademark.