well, i'm not experienced at using libpd in an application but i've definitely researched the topic pretty thoroughly. špeter brinkmann is the obvious expert here to talk to. so here's what i know:
libpd only uses vanilla objects, although expr~ was recently included in that group. it can be extended by including other libraries into libpd as far as i'm aware. i'm definitely aware of at least two cases where the cyclone library has been compiled for use with libpd.
so, if your plan is to use it locally with your friends, this should basically work fine. also as far as distribution via the different stores, there should be no issues with offering a product for Android via Google Play.š
however, if you are releasing this product on the iTunes Store, Apple has a restriction that does not allow third party libraries to be included that have GPL licensing. since the vast majority of PD libraries have this licensing on the binaries, it means you will need to recompile the desired libraries from source and change the license in order to put the product on the store. BSD or MIT licenses seem to be preferred. without this license change, i don't think that you can even offer the app for free, but i'm not sure about this.
if anyone else has more accurate information, feel free to confirm, clarify or refine.
hope this helps,
scott