Is the word principal the same in Brazilian and European Portuguese?

Yes

The word "principal" is identical in meaning, spelling, and grammatical function in both Brazilian and Continental Portuguese. The only difference is pronunciation. In Brazilian Portuguese, the "l" at the end of a syllable is typically vocalized, sounding like a "u" (e.g., prin-ci-pau). In Continental Portuguese, the "l" is a "dark l" [ɫ], where the tongue approaches the roof of the mouth, maintaining a more distinct "l" sound.

Brazilian Portuguese Examples:

1. O principal motivo do atraso foi o trânsito. (The main reason for the delay was the traffic.)
2. O ingrediente principal desta receita é o leite. (The main ingredient in this recipe is milk.)
3. A nossa principal meta é aumentar as vendas. (Our main goal is to increase sales.)
4. Ele é o principal responsável pela organização. (He is the person primarily responsible for the organization.)
5. O principal problema é a falta de tempo. (The main problem is the lack of time.)

Continental Portuguese Examples:

1. O principal objetivo desta reunião é definir prazos. (The main objective of this meeting is to define deadlines.)
2. O elemento principal da trama é o mistério. (The main element of the plot is the mystery.)
3. Esta é a nossa principal via de acesso ao centro. (This is our main access route to the center.)
4. O principal erro foi a falta de comunicação. (The main error was the lack of communication.)
5. O açúcar é o componente principal deste produto. (Sugar is the main component of this product.)