Is the professor positive toward me?
In the US and some other places, graduate (and other) admissions is handled by the university itself in coordination with an academic department. They are not under control of individual professors. Therefore, in such places, you need to deal first with the admissions system, and than with a professor. 

Depending on how you phrased your letter he may just be informing you of the rules. 

You could, of course, send a letter to professors expressing your interest, telling them that you are applying through normal channels and asking if they are considering taking on students for advising. Such a letter should show some knowledge of the research interests of the professor and your own matching background. 

For your specific question, I think the professor is being as positive as he can be. Don't take it as a negative. 

Also, depending on the field, the professor may not be responsible for choosing graduate assistants. Again, it may be a university or department decision. In some other fields, the professor, if grant funded, can staff his/her own labs. In mathematics, for example, while you have a specific advisor, you may 'work for' the department, not that professor.