This is going to be old territory for some of my long-time readers. But recent events show that the myth of "webinar's protected status" is preventing people from getting what they want from providers.
One of my clients (a very large company) got into an internal email chain about whether they can use the word webinar in call scripts. They said that operators hosting web events had told them they could not say "Welcome to our webinar" in the introduction, because the word was copyrighted.
I'm no lawyer. I took one introductory business law class in college, and that was a heck of a long time ago. But this is just silly. First of all, you can't copyright a word. Look it up at the Copyright Office website. You can copyright literary and recorded works, graphics, architecture, and choreography. You explicitly cannot copyright "titles, names, short phrases, and slogans."
So let's forget about copyrights. The proper thing to look for is trademark ownership. A trademark (or the related issue of service mark) can be applied to "a word, phrase, symbol, or design" or combination thereof "that identifies and distinguishes the source of the goods of one party from those of others." That's from the US Patent and Trademark Office website.
In general terms, you have to come up with something that identifies your version of the more generic thing as being specific to you. That's why the formal legal versions of trademark usage always use the trademark name as an identifier to a generic term. "Enjoy the benefits of a Kleenex tissue." "Make your copies on a Xerox copier." Kleenex and Xerox are trademarks. Tissue and copier are generics. Once enough people start using your specific term as the generic, you are in danger of losing your trademark protection. Thermos, aspirin, and cellophane all started out as trademarks and now have no protection because they were accepted as generics. Really successful brands face this concern after they have spent years trying to achieve that level of visibility. Google and WebEx are both slightly worried at the moment about people "googling each other" or "hosting a webex." The kind of problem you dream about having when you start out as an entrepreneur!
Anyway, the US Patent and Trademark office has a handy little search engine you can use for free to check on existing or past trademarks. Put in "webinar" and you get 9 hits in combination or alone. The word by itself accounts for three instances. All are labeled as "DEAD" - meaning the applications have been abandoned or declined.
If somebody wanted to try for a trademark on the word now, it would be awfully hard to overcome the generic status of the term. There are untold thousands of usages in print, radio, and electronic communications... All without any branding or trademark identification. And of course we just had Merriam-Webster grant the word official status as an English common noun.
Given that, I would argue that you are pretty darned safe using the word "webinar" any time and any place you want. Just as long as you don't claim it as your exclusive property. Opposing points of view are welcome... Especially if you currently claim to own the trademark on the word!
For those who want to track back posts on this subject, see the following references:
We Oppose A "Webinar" Trademark (Conferencing News)