Side quest that says "No more than 3 progress tokens can be played on the current quest each round". Does that also include the active location? For example, if after quest resolution I'd were to put 5 progress and there is an active location with 8 quest points, do I place 5 or 3 tokens on that location?

I don't think the active location comes into the equation. You can clear it normally regardless of the number of progress tokens it requires, but then you're limited to only 3 on the actual quest card.

''Current quest'' means any quest or side quest card, not locations.

Doesn't Core Set Legolas' ability allow him to put progress tokens on the active location though? and Legolas reads: "...place 2 progress tokens on the current quest" ¿?

Doesn't Core Set Legolas' ability allow him to put progress tokens on the active location though? and Legolas reads: "...place 2 progress tokens on the current quest" ¿?

Player cards that direct you to place progress on the current quest always go through the active location first.

Side quest that says "No more than 3 progress tokens can be played on the current quest each round". Does that also include the active location? For example, if after quest resolution I'd were to put 5 progress and there is an active location with 8 quest points, do I place 5 or 3 tokens on that location?

5 progress. The active location is not the current quest.