, are you darkcity from the forums? :D <3
The package is 19mb and 44mb unpacked. It is 0.4.10 that I ported myself a few days ago. Works flawlessly. What I might do is make a script where if the user runs lmms, it will check if they have it installed or not, and if they don't, it will install it from the pet package that I will store in /usr/share/pets/ locally. That way, over half the space would be saved.
In all, it will probably increase iso size by about 5-10mb.
As for how many people will use it, I am not sure. It is probably the number one Linux music composition program though, so I would say it is moderately useful.