Hi, is there some overall general information about how to go about using libpd / Pure Data on an iOS app for the AppStore? I've heard rumours that Freeverb~ for instance cannot be used as-is due to some fancy licence that means that if you use freeverb~ on an app for AppStore, the AppStore will reject it.

Is there some list of free-to-use/which-license-to-go-with type information on specific PD Externals, for instance?

We all know that the AppStore is notoriously strict with licenses, so it'd be lovely to find some discussions on what is allowed and what has to be, basically, re-scripted.

I think GPL and LGPL aren't ok for the AppStore. BSD should be ok.

I've kind of been thinking about making some simple but nice sounding Vanilla reverbs that can be used for this sort of thing.

I don't think Freeverb is that great anyway. It sounds good for a Schroeder reverb, but there are better things out there.

acreil, please do. The reverbs in the audio you've posted before have been really nice.

acreil, that would be wonderful. always loved your reverbs

Well, that's a big project still, and more of a long term goal than anything I can get to immediately. But it would be nice to have a sort of toolkit with various (documented!) abstractions that anyone could use to build reverbs of arbitrary complexity.

Ok, one more question:

It seems that Pure Data is GPL (?) - there are people around me insisting that every single piece of scripting made with PD, for use in libpd, for android + iOS, that the source codes would have to be released for a commercial product? Is this true?

No pd vanilla is bsd, pd extended has many gpl libraries in it. expr is lgpl. Also you cannot release things under the gpl license on, say, the apple's app store because it has it's own license that conflicts with the gpl (but not bsd)
see here for an overview http://www.tuaw.com/2011/01/09/the-gpl-the-app-store-and-you/
and I think that if you use gpl libraries (e.g. externals) in your product then you need to also distribute the pd files (source). Or you can give information about where they may be obtained. However I don't think you need to distribute externals you write because the pure data API is bsd.
here's another helpful link http://www.linfo.org/bsdlicense.html

as far as which licenses apply to which external, usually the licenses are distributed with the libraries. check in your pd distribution, for instance in the extra folder of pd extended. There should be files like LICENSE.txt in most of them
btw you can still sell gpl software (but everyone else can sell your gpl software also) https://www.gnu.org/philosophy/selling.html you just need to distribute the sources as well (see for instance Ardour)
http://www.techrepublic.com/blog/linux-and-open-source/is-it-legal-to-sell-gpl-software/#.