Underwriting rules for non-com educational stations apply only for stations receiving consideration to the radio station from a sponsor. Consideration can be money, barter-trade, or even an expectation worked out between the sponsor and the station of a favorable report or review on the business. If there is no consideration given to the radio station in any shape or form, it is NOT Underwriting.
Thus, in this case, the sponsor is apparently not giving any consideration to the station, therefore it falls into a NEWS/PROGRAM FEATURE catagory. For example, you can rave, endorse, tell people to go down to movie theater (movie review), or otherwise provide a call to action and express qualitative judgements all you want and not violate FCC rules if it is part of a program, news or news feature.
You can also tell your listeners to go down to the radio stations' Listener Appreciation Party or Dance and talk it up all you want assuming your non-com is a non-profit entity, which they all typically. Proceeds or profits must go towards the station.
Also, if the sponsor is a 501c3, non-profit corporation, school district, University, or governmental entity there are no Underwriting rules to follow.
The Commission has determined that a lengthy underwriting spot is contrary to their rules, so most non-coms limit the spot time to 20 or 30 seconds. A non-underwriting spot can typically be 60 seconds long, with full call to action, qualitative verbiage, flowery adjectives, inducements, and other such normal Commercial-sounding script. However, to keep things in conformity with the for-profit spots, a station may want to standardize their rules to protect their air sound and keep it consistant, regardless of type of client.