Whatever it was, it doesn't look like it went very far seeing as how they didn't have a script. My guess is the deal just fell apart and nothing else came of it. Given the date of the article, I wonder if they were trying to to capitalize on the success (?) of The Girls on the Beach.
There was a plan as early as spring '64 to create a Beach Boys film vehicle, AIP announced in the press that year that they were developing one, then apparently Murry killed that by insisting the Beach Boys control 100% of the publishing on the soundtrack music. The Girls on the Beach film was the fallback plan while they worked to put together a second deal with a different studio. The article above shows that it didn't get far. Mid 1964 to mid '65 was really the Beach Boys window to pull this off, after that their popularity wasn't strong enough from a teen idol standpoint. BTW the Beach Boys were the highest paid act in the TAMI Show film, and in fact the contract they insisted on is what got them cut out of later prints as Dick Clark who bought the rights to the re-release in the late '60's or early '70's could'nt re-negotiate their orig. iron clad demands from '64 making it easier to just not have them in it. then all subsequent prints had them missing, sparking all kinds of theories as to why...but the truth is it was just money.