Thank you!The words of the scroll are:
San ka shou ten ka shun. The mountain flowers laugh, the world is spring.
I cannot see any author. The words to the left are : Oubaku kou rei sho. Written by order by Obaku (a school of Zen).
The Dai I (explanation) is : the flowers bloom with unobstructed mind, the little birds too warble with unobstructed mind, with the exchange of such mind the joy of the new year overflows.
The red seal to the right says: Rinzai Shoushu (Rinzai School of Zen).
The red seal below is Oubaku sanshu (the head of the Obaku school).
The seal in outlined red is kou rei (by order)
That is a rough translation. I would welcome someone to render it more felicitously.
Thank you!The hiragana gives the reading of the phrase
Sanka warau, tenka no haru
Kōrei (亘令) is the name of the priest (of the Ōbaku zen school) who presumably wrote the scroll. He died in 2014. Sho (書) at the end of that sentence just means "written by". So, "Written by Ōbaku Kōrei".
For the translation of the meaning of the expression, I think yours is as good as it might get. Something about the unconscious or un self-consciousness of the bird singing, and the flowers blooming, being a joyous harbinger of spring.