GPL is such offensive license, but now is 2014 - I don't understand why people still use it ?
Would it be wiser to specify whatever you need from license and make your own license for that ?
Like you said - you're afraid of dosbox selling - why not to specify - before you make commercial application from dosbox, you need to have written agreement with dosbox developers.
Now it looks like you're afraid of something , but you're not brave enough to specify what you're afraid of and just trying to hide behind a lot of crappy legacy text which no one actually understands.
Btw - GPL license does protect dosbox code, but it does not restrict of selling commercial dosbox. For example - if I'll take source codes for dosbox, make my own variation and start to sell it - it's ok.
You can request my own source code of dosbox, and I must provide it to you - but there is nothing specified about delivery costs or delivery time.
You request new dosbox source code from me , and I will reply to you that I'm afraid of competitors (he he) and won't send you that one by e-mail. And since I'm leaving in long distance - you will need to pay off my travelling expenses for delivering you dosbox source codes. (Machine fuel price for driving to post office, postage costs and so on...). Of course I will send you my most expensive way, and will probably forget important parts of source code to be included. Since I'm really busy guy you will receive within one year that project, and most probably I will have another major version already deployed.
Good luck with fighting about license terms and conditions and hiring more lawyers.