In most cases, used software can be sold if it is no longer needed – but there are some strict requirements for it to be legal. The reason for this is that you don’t purchase software outright, you purchase a license to use the software and the publisher retains the ownership of the copyright.
The seller must give the purchaser the original CD or DVD media, the serial number and a transfer of ownership of the license. Then the seller must erase the software from their machine(s), because they have given up the license to use it. The original owner cannot continue to use the software. If there were terms and conditions on the original license (such as Eductational versions for full time students only) then these license terms are binding on the new owner as well.
Some companies have additional rules about how you need to fill out forms and register the transfer of license with the company. A few companies charge money for the transfer. Check the software manufacturer’s website for specifics.
One questions that gets asked is if someone upgrades from Version 4 to Version 5 of a software program, can they sell off the Version 4? The answer is no, because there is only one license to use the software, and the upgrade price only moves that one license to Version 5, it doesn’t generate a new license – so Version 4 cannot be sold
Another question is if someone buys a Family pack or Multiuser pack of software that has installs for three computers (for example) can they use one and sell off the other two installs? The answer again is no because the terms and conditions of the license of the reduced-cost multiple install package usually state that all three installs must be under the same roof or within the same company or used by the same person or family. Check the exact terms of the license.
Just to cover, the term ‘sale’ also covers giving away or lending or any other method of allowing another person to use the software.