The Prof. clarified this is mail in CTamil forum "Dear colleagues,
Just for the record, I said that Subrahmania Sastri considered parts of Tol. as translations of Sanskrit texts, which is not correct because
the interection of those times was connected not with translations, but with rendering etc. And I did not say that Tol. is not dependent on Sanskrit sources (because it is). My idea was that in spite of this Tol. described not S. but Tamil language and used the achievements of Sanskrit linguistic schools (not to invent a bycicle), which needed not only knowledge but a lot of thinking etc.
With best regards, A.D."
First people have to understand is the Tamil and sanskrit are from totally differnt language chains. So to apply some of the rules of one language chain in another you need expertise in both and lot of creativity. Tamil was not a written language..the accepted explanation is writing came in Ashokas period from the north. It is expected that influence of Sanskrit,Pakrit,Pali would be present in such early grammer work.
The author has just quoted one paragraph to argue Tolkapiyar is brahmin, I had read few authors quote some other pages to show he is a Jain. One thing we fail to realize when we argue is probably the person was well versed in both Vedic ,Jain , Buddhist philosophies. For eg. we find traces of all religion in Kural and still fight is going on whether he is Hindu or Jain.
Any proper critique on Tolkapiyam would say that it had influences of Sanskrit. As Dr.Zvelebil points out Tamil and Sanskrit didnt develop in isolation. Tholkapiyam was influenced by Sanskrit and rig veda earliest sanskrit work has very high amount of Dravidian root words.
Just bcos the earliest literature of one language was influence by any other Language doesnt take away much from the language. Tamil was just a spoken language at least for 3 centuries b4 tolkapiyam.
It time people understand difference between influence and being mother language. Sanskrit is dead bcos it didnt adapt with times(except for one remote village where they speak in sanskrit). Tamil is still a spoken language bcos of its ability to adapt. This means it has taken in lot of influence from lot of languages to survive this long. Esp when you consider Tamil was not a major court language in Tamil nadu for centuries.