The current plan is to have the full game professionally localized into many languages (likely including Portuguese) for the full release.
That said, the game can already be fan-translated without the need for mods, as all of the localization tools are already implemented. There is a game-messages.csv file in the main directory. This has several columns - one for raw text (Original) and one for the English displayed text (en). Replacing the text in the "en" column will change what text is displayed in-game by default. Translating that column will mean all of that text will appear translated in-game for anyone who replaces their game-messages.csv file.
If a special font is needed, renaming any font to "VCR.woff" and replacing the file of the same name in the fonts folder will change the default font.
There is some text which is not included in the "Original" column of the csv file. You can add any text to a new cell there, and any translated text to the eng column to change any text in-game which matches (ie. if the words "You found" are not in the csv file and not being translated in game, you can just add that and its translation to a new cell in the original and en columns, and then they will appear translated in-game).
Since it is just the csv and a font that need to be replaced for someone to get the translation, you can easily make a drag-and-drop patch for any language.
I am also open to including any fan translations languages in future builds of the demo until the official translation is created.