Is it possible to make a separate deal with the client regarding the software licensing terms?

[f461a0d5]

I am making a pretty "important" (as in complex) software for a decently discounted price, is it possible to establish a deal where the freelancer keeps the copyright and the client gets a license giving him full rights over the software?

this way it would make economical sense for me to maintain the software (free of charge) even after the contract is long fufiled.
I want to so mostly because the client lacks an IT departement and because I would like to have the software in my portfolio as well. also so many things could be added or reused from the software in question and since I take copyright very seriously doing all the things I previously mentioned would not make economical sense if I just applied Upwork default terms.

[spectralua]

Sure, you can make additional agreement.