This work was first published in 1894, so is in the public domain in the US and Canada, and any other countries where copyright expires 70 years after publication, or 50 years after the composer’s death.
The edition is my own, however the actual music is Sibelius’ own arrangement. If you want to perform this music commercially, so long as the composer’s work is in the public domain in your country, you don’t need to give attribution to AltoClef as the editor.
Each document is a pdf. Your computer shouldn’t flag the file as malware, but if you are concerned, run a quick scan with any antivirus software after the files have downloaded.