Originally Posted by EcoSee
I added the footer tag crediting Pixelpost with a link back to the main site. In the future there will be more of an "about us" page where I will expand that explanation even further.
Seems ok to me now, assuming that the copyright notice of Pixelpost team is still intact in the source code of the pixelpost package and the indication to the GNU General Public License is provided.
GNU General Public Licence states out clearly how you have to deal with copyright and license when conveying modified source versions:
4. Conveying Verbatim Copies.
You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.
5. Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:
* a) The work must carry prominent notices stating that you modified it, and giving a relevant date.
* b) The work must carry prominent notices stating that it is released under this License and any conditions added under section 7. This requirement modifies the requirement in section 4 to “keep intact all notices”.
* c) You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
* d) If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.
Following these terms of GNU General Public License you cannot restrict the license of Pixelpost. And your modified source code must be available for your customers, with a download link for example since you don't offer an FTP account in your plans.
Besides you should check all Addons you are offering with your package for copyright and license and make sure that appropriate credit is given.
Attention: if there is no License attached to an Addon, it does not mean that it is completely free for (ab)use, but contrariwise the license is restricted to "all right reserved". So better ask the addon authors if it is ok to offer their work in your package. As far as I can see from your website it concerns at least Dwilkinsjr for his Auto-Resize-Addon, Jaywilliams for the Adobe Lightroom Plugin and Dennis for the Google Map Addon.
And better ask Jaywilliams if it is ok for him to be mentioned like this on your site, it looks as he is part of your developer team...