Maya is usually sold for several thousand dollars. Alias|Wavefront provide a free version of it called the PLE (which you have got). The PLE has the writing over the screen (called a "watermark") to stop people using this free verion for commercial production. You can't get rid of it. As another precaution the PLE also saves your work as a special file type which can only be read by the PLE. If the PLE didn't have these limitations there would be no reason for anyone to buy the full version and Alias|Wavefront would go broke!!
Take a glance at my <a href="https://forums.simplymaya.com/showthread.php?s=&threadid=9428"><b>Porsche 959</b></a> WIP