I work for a software / design firm and I recently found out that our "in house" CMS is actually [based on software] licensed under the GPL Ver 2. I would like to know if it is ethical / legal to be selling this to clients.
Here's a passage about GPL from Wikipedia (emphasis mine):
The terms and conditions of the GPL are available to anybody receiving a copy of the work that has a GPL applied to it ("the licensee"). Any licensee who adheres to the terms and conditions is given permission to modify the work, as well as to copy and redistribute the work or any derivative version. The licensee is allowed to charge a fee for this service, or do this free of charge. This latter point distinguishes the GPL from software licenses that prohibit commercial redistribution. The FSF argues that free software should not place restrictions on commercial use, and the GPL explicitly states that GPL works may be sold at any price.
However, if your company is distributing the software under another license not compatible with GPL, then they're violating their license.
I'm posting to my blog the questions I've answered on StackOverflow, which earned the "Good Answer" badge. This was my answer to "Is This Legal? (GPL Software/ Licensing Issues)"