TDS on customized addition to readymade computer software

Very often businesses get some customisation done in the readymade licensed softwares (like Tally) as per the requirement of business accounting/billing as such softwares have their own default formats, layouts and interface settings which may not be suitable for billing/accounting purpose. Such customizatiins, some times, are done by independent developers/programmers (authorised or not by Tally company).

My query is, under which section TDS is applicable for such customization of software if contract is given directly by business to the vendor? And what if sub-contracted by software vendor?