You don't take ownership if you download files from SharePoint. If you're using the SharePoint CSOM API, you're code look like this:
using (var clientContext = new ClientContext(url))
{
clientContext.Credentials = creds;
var list = clientContext.Web.Lists.GetByTitle(listTitle);
var listItem = list.GetItemById(listItemId);
clientContext.Load(list);
clientContext.Load(listItem, i => i.File);
clientContext.ExecuteQuery();
var fileRef = listItem.File.ServerRelativeUrl;
var fileInfo = Microsoft.SharePoint.Client.File.OpenBinaryDirect(clientContext, fileRef);
var fileName = Path.Combine(filePath,(string)listItem.File.Name);
using (var fileStream = System.IO.File.Create(fileName))
{
fileInfo.Stream.CopyTo(fileStream);
}
}