What is the difference between oscailte and ar oscailt? The sense I get is that, during business hours, a shop is ar oscailt, but the window in that shop is oscailte (?)

is there an equivalent distinction drawn with dúnta (there doesn't seem to be, that I have found)?

I'm not sure there is a clear distinction.

It's an interesting question.

I think you could say
a) Tá an siopa oscailte idir a naoi agus a cúig
or
b) Tá an siopa ar oscailt idir a naoi agus a cúig

I think I'd prefer b) but I don't know why.


oscailte [aidiacht den tríú díochlaonadh]
ar oscailt, ar leathadh; gan cheist gan cheilt (dúirt sé amach go hoscailte é).

"Tá an scannán ar siúl idir a naoi agus a deich "

Maybe it is more natural as it is in a current state of openness, whereas a verbal adjective is more the state that has come from a transformation and is finished -in that sense the shop is not 'opened' but is 'open' between the stated hours

yeah...that's what I meant...it's also a figurative "open"...a shop can be "open" on a hot day and yet have all the doors and windows closed to keep in the air conditioning...