No. Colleagues who open your workbook can see the chart and update the plan in the table (dates, progress, new tasks) without a license, and the chart redraws for them. Viewing never uses a device slot.
A chart you made with a license or during the trial keeps its full look for them, including dependencies, colors and all tasks. Changing any of its formatting, such as colors, the theme or the critical path setting, needs a license or the trial.
What they do need is the SimpleGantt add-in in their Excel, because the add-in draws the chart. Adding it costs nothing. In a company, the IT admin can deploy it for everyone; see Deploy SimpleGantt in Microsoft 365. People without Excel get an export instead: PowerPoint, PDF, image or an HTML file.