This might depend on the legal jurisdiction that currently applies in the country where the licences were purchased.
Within the EU, my understanding is that if you have purchased a perpetual license for some software, you can sell (or give) the license to another legal entity, regardless of the T&C within the licence. There are a few court decisions that support this view.
In other jurisdictions the licence T&C may govern what you can do.
One way to find out what applies in your area is to Google for licence resellers and ask if you can sell your licences. However, be aware that the older the software is, the lower the value of the license - SQL 2005 may now have a zero resale value.
Original author: SQL Server FineBuild 1-click install and best practice configuration of SQL Server 2017 2016, 2014, 2012, 2008 R2, 2008 and 2005. 1 Dec 2016
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Disclaimer: All information provided is a personal opinion that may not match reality.
Quote: "When I give food to the poor they call me a saint. When I ask why they are poor they call me a communist." - Archbishop Hélder Câmara