Obsolete is a verb, but it is a poor choice. A better choice would be obsolesce, as in: "LESS.js will obsolesce CSS". This is because LESS.js won't obsolete CSS, but it may well start the industry on the path. Obsolete has a feeling of immediacy to it, and obsolesce has a feeling of lethargy or a gradual process which is why it's the better choice.
It's an opinion, take it with a grain of salt.
(BTW, I dislike MW because it takes all nuance out of the language and dumbs it down to an inexpressive mess.)
Obsolete is a verb, but it is a poor choice. A better
choice would be obsolesce, as in: "LESS.js will
obsolesce CSS"
"Obsolete" is the correct word because it's a transitive verb (eg, [subject] obsoletes [object]), while obsolesce is an intransitive verb (eg, [subject] obsolesces).
"Mr. Wolfe is in the middle of a fit. It's complicated. There's a fireplace in the front room, but it's never lit because he hates open fires. He says they stultify mental processes. But it's lit now because he's using it. He's seated in front of it, on a chair too small for him, tearing sheets out of a book and burning them. The book is the new edition, the third edition, of Webster's New International Dictionary, Unabridged, published by the G. & C. Merriam Company of Springfield, Massachusetts. He considers it subversive because it threatens the integrity of the English language. In the past week he has given me a thousand examples of its crimes. He says it is a deliberate attempt to murder the — I beg your pardon. I describe the situation at length because he told me to bring you in there, and it will be bad."
MW adds practically any word that someone uses, ever. And Wiktionary? Come on.
If you take a gander at WordNet or even OneLook (searches multiple dictionaries), you'll find that the majority list obsolete only as an adjective, including Webster's 1828.
However, I concur that obsolesce would have been a better choice.
Dictionaries are historians of usage, not legislators of language. If the communication is clear, which in this case I think it is, then I don't see a problem.
http://www.merriam-webster.com/dictionary/obsoleted
http://en.wiktionary.org/wiki/obsolete