The case of the Kansas sperm donor who may be required to pay child support, among other expenses, because he didn't donate through a doctor would probably play out very differently in Texas.
Although Kansas law requires that artificial insemination be carried out by a licensed physician, the donor in the Kansas case simply donated his sperm to a same-sex couple, without going through a doctor. The couple, who had advertised for a sperm donor on Craigslist, and the donor signed an agreement terminating the donor's parental rights and stating that he wouldn't be liable for child support, but a Kansas court ruled that the agreement was invalid because the transaction (i.e. the sperm donation) wasn't performed by a doctor.
Paternity only became an issue when the child's biological mother ran into financial and health issues and applied for state assistance. The child's "other mother" has no legal recognition in Kansas, so the state went after the sperm donor to seek reimbursement for the financial assistance provided by the state.
In Texas, there is no longer a requirement that the donor provide sperm through a licensed physician. The law, in fact, is quite clear as to donors, both male sperm donors and female egg donors: a donor is not the parent of a child conceived through assisted reproduction.
Still, laws regarding assisted reproduction have a long way to go to catch up to the technological and cultural changes in our society. Though the law addresses who can be considered a parent of the child, it still does not address important issues such as the ownership of embryos and regulation of the medical procedure.
Regardless of how the Kansas case shakes out, and regardless of the current state of Texas law, a potential sperm donor in Texas would be well-advised to check with a lawyer before making a donation.
UPDATE: The Topeka Capital-Journal reported on March 6 that an attorney representing the child has asked the court to conduct an evaluation of the child, now 3, to see whether it would be in the best interests of the child to introduce the child to Mr. Marotta.