Nowhere near, I'm afraid. Blockland is proprietary software. If it was under the GNU GPL, you technically could sell it, just as long as it remains open source and under the same license. In this case, the license to Blockland states something somewhere around the lines of "All derivative works are owned by Blockland", meaning that technically anything you made isn't even yours. So it is quite illegal against the licensing terms.
First of all, (s)he spoke about add-ons, not Blockland itself.
Secondly, Ibrown town, but I think that in, for example, Sweden, that line simply doesn't have any effect as you can't transfer copyright itself according to the copyright law.
