They are providing debian installer files from their website.

• Ubuntu 32: http://www.codeandweb.com/download/texturepacker/2.4.0/TexturePacker-2.4.0-ubuntu32.deb


• Ubuntu 64: http://www.codeandweb.com/download/texturepacker/2.4.0/TexturePacker-2.4.0-ubuntu64.deb

The image they use to show they have an Ubuntu download suggests it is for 11.04 but that does not mean you can not install it in 11.10, 12.04, 12.10 or 13.04. Let Ubuntu Software Center open the file and see if it installs.

If this works... no need for an alternative.
If not please add it into your question and we can try to work from there ;)