protect demos: time out, insert noise, cripple the image with a generated image from jit.lcd (you don't say if its audio or video). more secure if your demo is different from your purchased product.
we tried pace for a while, but is so absurdly expensive for small timers, that it's not worth it. I rolled my own challenge/response thing, but it involves some custom externals and php.
Really, a serial number is mild protection, but so easily circumvented, it's somewhat pointless.
You may want to cripple the demo and just make the purchased download cp-free. Unless you expect to sell a lot, it's easier for you and your customers. We use cp on our video app (lividinstruments.com) becuase we don't have the personal connection to our buyers that I had with previous programs.
My approach for my MIDI-only app was to have my demo timeout (no input) for 30 seconds every 5 minutes or so, then timeout after an hour, requiring a quit/restart. This seems sufficiently annoying. The demo does not currently "die" after X days.
I use Kagi for sales, but I email the app directly. This does have its up/down side, might change that soon. I must ask Kagi about their java implementation to see if it's embeddable in Max.
The purchased app is a separate app (so no "unlocking" the demo), and I embed the registered user's name into it in a way that will be difficult to find & change, so if it appears on limewire etc, at least I'll know who let it loose, for all the good that will do.
If you wanted to lock it down further, you could look at tying it to a specific machine's MAC ethernet address, would probably be best done via java. Ultimately, I think this is more effort than it's worth, and a real pain for users.
As far as preventing users examining the .mxf or otherwise reverse-engineering the app, it's only possible to make it more difficult. Let's not discuss this aspect on the forum. I'd be all in favour of an encrypted standalone format, but that's certainly not on C74's roadmap I believe.
Regarding recording audio, I agree that anybody with a brain could keep using the demo without having the need of buying it..
I'll put a buzz here and there every 30 secs. so it will be very annoying and unpractical to use the demo for other purposes than exploring its functions.
The retail file will be different and downloadable only @ kagi store.
I guess nobody (or very few) will try to crack the mxf file becouse the retail price will be so low that it would be unlikely worth the time and talking of complicated patch, I can assure you that my app is an hell :P
My only concern is that I'll se the retail program on a p2p in a few weeks.