The word ‘Shudra’ has been a subject of dispute since the time when some reformers started ridiculing the cast system. Of course, the present day cast system cannot be accepted. Swami Dayanand Saraswati is one of the names who fought against the prevalent system of his time. But, he also indicated the evidences, which had shown that the cast system was based on gun karma svabhava (quality, deeds and nature) of a person.
But, here I found some gentlemen quoting a line from Satyarth Prakash, one of the popular treatises of Dayananda, in which he said that Shudra should serve other varnas, and trying to prove him a castist. But, perhaps they forgot to read the other part of his book, in which he clearly said that a Shudra can become a Brahmin and similarly a Brahmin can become a Shudra according to the deeds. A long description has been written by him to prove that the varna system is according to deeds not according to birth. According to Satyartha Prakasha and his other books, Shudra is a person who is not able to do the mental work (which can be from any family) but can do the physical work. About other varna, Brahmin is the person who is learned, Kshatriya is the person who is warrior and Vaishya is the person who has the ability to do the business. A Brahmin’s son or daughter can be Brahmin, Kshatriya, Vaishya or Shudra, and similarly the child of other persons of other varnas can be of any varna. The person who has the physical ability and not the mental efficiency often serves the persons with mental ability, and the same thing Swami Dayanand described about Shudra.
So, the Shudra according to Swami Dayanand has nothing to do with its pet definition. It is Arya Samaj founded by him where Shudra can also become a Pandit.