Honda is indeed sponsoring the latest season:
Honda has joined as the presenting sponsor of the highly anticipated sixth season of Community, premiering exclusively on Yahoo Screen on March 17. As part of a one-year, online video upfront program Honda will have several integrations in Community as well as pre-roll video ads on new episodes and series highlights. Additionally, Honda will run premium display and audience advertising across our extended network throughout the year.
The FCC regulations indicate that sponsorship notice is mandatory (at least for broadcast/cable):
The sponsorship identification rule requires the identification of the sponsor of any cablecasting that is presented in exchange for money, service or "other valuable consideration."
However, it may be that Community is now exempt from some of these rules since it is no longer distributed via television or cable networks. For example, regulations about "Objectionable Content" have a specific exemption for Internet tv shows:
It does not apply to video transmissions delivered over the Internet or via computer networks.
Personally, I thought it was really well done and actually enjoyed it quite a bit. It was creative, humorous and fit with the flow of the show instead of being forced and awkward.