Yes, it is legal to download ArcGIS 10.6 for free as a trial version from the official Esri website. Esri provides a 60-day free trial for ArcGIS 10.6, which allows users to test the software and its features without paying a dime.
Many searchers later discover that the personal license is so inexpensive that it effectively works like a long-term free option compared to the commercial price ($1,500+). Esri occasionally runs free month campaigns for personal use—worth checking. download arcgis 106 free