Category name "Development" was translated into "Programming" (Programowanie in polish), which doesn't make almost any sense in many cases. IMO the best replacement word would be "Designing" (Projektowanie in polish)
Even after two years, this is still valid. You can contact the polish translation team at transifex[1] and discuss this with them. Other than that, this bug should be closed. 1 - https://www.transifex.com/organization/xfce/team/16840/members/pl/
As stated in c1, https://www.transifex.com/organization/xfce/team/16840/members/pl/