PdfRenderer uses Ghostscript. Ghostscript v9.06 and earlier are licensed under the GPL v3; 9.07 and later are licensed under the AGPL v3.
Therefore, the PdfRenderer binaries are also made available under both the GPL v3 or the AGPL v3, as PdfRenderer (in its current form) links dynamically to the Ghostscript library.
While the GPL v3 and AGPLv3 do not allow us to license the binaries under the MIT license (since they are derivative works when used with the ghostscript DLLs), we can license the source under the MIT license.
This allows any future user to take the source code and modify it to either
Ghostscript has serious issues with multi-tenanting, and eventually works itself into an invalid state over time, with some PDFs. PDFium might replace one set of bugs with another, but it seems like a very useful experiment, and would certainly fix the licensing issues (as would using Ghostscript in a separate process).
** Be aware that (unlike other plugins), the use of Ghostscript places restrictions on the binaries of any code that uses the PdfRenderer plugin; because it too becomes under the GPL (or AGPL), in addition to any other license it is under.**
If you are not distributing binaries of your code which uses the PdfRenderer plugin, or are only using them on your web server, it is unlikely you need to be concerned about this.
You will need to comply with the terms of the AGPLv3
If you are interested in funding development of a GPL-free version, please contact support@imageresizing.net.
To sum up: Compiled versions which use Ghostscript are under the GPL v3 or AGPL v3. Source is under MIT, GPL v3, or AGPL v3, your pick.
Copyright (c) 2012 Jason Morse and Lilith River
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