My source is the actual copyright in the TAS credits, right there onscreen. It says "(c) COPYRIGHT FILMATION ASSOC.-NORWAY PROD. 1973." Paramount didn't have a copyright on the original episodes, so I figured it didn't own them. Although it did have a copyright on the Foster novelizations, which is confusing.
Paramount didn't have a copyright on the original episodes? I know there was an issue with their copyright of the Desilu-produced episodes in the 1970s, but Paramount (Television) was able to reacquire their ownership and copyright them, which is why they now bear the copyright date of 1978.
But, that wasn't my question. I wanted to know if Paramount bought the rights from Roddenberry/Norway at some point, which your statement implied they did sometime after the animated series.
I believe you're right that Norway doesn't get credit on anything past TMP, but the budget for TUC does include the language "RIGHTS PURCHASED, GENE RODDENBERRY, (NORWAY CORP.)" for the price of $1,000,000.